You need to consider the purpose of your ground.

All the equipment in your shack that has 3 prong plugs is safety grounded by modern 3 prong house wiring.

If you are doing it for lightning, you should be concerned about grounding at your suppressor and the suppressors characteristics.
The impedance of that ground better be lower than the path into your house or the lightning will just be "invited" into your shack.

If you are after the "mythical" RF ground you are dreaming unless wire lengths are short.

If you are trying to equalize potentials between the various boxes in your shack, then a bus between the boxes is what you are striving for.

Except for lightning or in the case of 2 wire plugs and house wiring, grounding has little functional value.  If you make sure common mode RF from antennas is controlled and you interconnect your system correctly, you will notice no benefits.

I have a multitude of radios and computers in my shack and don't have a big expensive ground system.  Everything works as long as my antennas don't have a common mode problem.  The antennas include coax and window line fed systems.  Several times I added new antenna, and when I was sloppy I had RF problems, but in each case attacking the common mode issue was the solution.

In the end most hams just ground things because other hams tell them to and the big bus bars and wires make them feel good.  So if you are in this camp, then just do what feels right.

Maybe consider using some single rectifiers in alternate packaging?

You must have a lot of room if you were running stud mounted rectifiers and are replacing with some sort of bridge in a big block package.

Modern packages are something like TO220 tab mounts (only bigger).  You could look thru the Digikey catalog or Mouser catalog and find something like that and mount single diodes on the heat sink.  Some diodes are available in dual center tap and you might be able to use both diodes in parallel since they are probably on the same silicon and well matched.

It would seem to me to be difficult to implement 2 miliohm resistors that are matched very well when wiring resistances might be of the same order.

Replace the feed line to your inverted vee with window line.  Add a 1:1 choke balun to the output of your autotuner.  It should work on most bands were the antenna is greater than a half wave.  If necessary fiddle the length of the window line to facilitate matching on as many bands as possible.

Consider using a wide range manual tuner with balanced output.

This is a tried and true system for a simple multiband antenna.  I've used it for years in many locations.  I highly recommend it.

If you are building a 6m antenna its pretty short, why not consider a center fed dipole?

You could mount in vertically or horizontally.

If you are doing SSB / CW, most of the world is Horizontal.

I dipole thumb tacked to the wall works well especially upstairs or in the attic.

You can bend a dipole and make it less directional.

An end fed system will always have matching and common mode problems and really only is necessary where the antenna must hang or work vertically and be fed at the end.  You would not do it for a half wave antenna unless there is a very strong reason because of mounting.

A better idea would be to add a three terminal low dropout regulator set to 13.8V.  You can still run it below that voltage but it is designed to have a low saturation voltage (PNP) device as the series pass element.

To really take advantage of the full output power you need a switching regulator.  You could use a buck step down and let it go to 100% duty cycle when the battery got below 13.8V.  If you use a FET switch, the full on drop would be low.

I will leave it to you to weigh the difficultly in EMI shielding and so forth.  It is not impossible since many modern radios have switching supplies.  It just takes a little care in packaging.

I think the diode Idea is just slightly better than a dropping resistor.

There is no problem driving high input impedance with a low output impedance.  It is the other condition of high output impedance to low input impedance that is a problem.

If you still think you need a high output impedance you could add a series resistor to the low output impedance and voila, its now high.

Seriously, you could use any low audio noise opamp.  You should look on the national semiconductor web site, they have a ton of old app notes and stuff like that.  I am sure there is something in there that will suit you.  Using an op amp will allow you to easily adjust the gain to whatever it is you need.

I mounted a small computer style 12V fan on the heatsink that sticks out the back.  You can get power from the accessory connector or the antenna tuner connector.

I noticed when I had my IC7000 in for some warranty work, they seem to have modded the firmware to make the internal fan come on when ever transmitting.  This also makes the unit much cooler.

You might want to consider these suggestions.

Also, you can safely test various power levels while observing the temp meter.  I have seen mine go to the red area before.  The rig does not immediately burst into flames.  I would also suppose that when it gets hot enough there is a shutdown that is activated.

You need to understand that modern power transistors can operate to 150 deg C junction temperatures.  Even 100 deg C is boiling, so the case temps can be 60 to 70 C and feels pretty hot to the human hand.  I don't advocate running equipment hot, but sometimes hams seem to have unrealistic expectations.

If you run windows programs under linux you either need to use WINE or a virtual machine with windows installed.

If using wine, go to winehq and check the data base for the programs you want to run and see if they have been shown to work.  Not all windows programs will work.  Especially if they use USB or hardware feature of the computer.  I think wine does work with serial ports but not sure.

A virtual machine allows you to run a copy of some version of windows on an emulated machine.  I have used VirtualBox and it works well.  It give the virtual machine access to the USB and other hardware of the computer.  You need a license or copy of some version of windows to install on the virtual machine.  Since many programs for hams run well under win95 or win98, I should think you could scrounge up a copy and install it in the virtual machine.  Since the virtual machine is a playpen, you don't have the crashing problems and security and update problems you would with a native win95 or win 98.

For dos programs, you can run them under DOSBOX in linux.

So you can use linux, you just have to use some work arounds to get there.

If you are installing Ubuntu, follow the directions in the installer.  Part of the process is partitioning.

Now the answer to the question is most likely EX4 or EXT3, these are the most common file systems used.  The swap partition uses a swap format.

Ubuntu install is pretty fool proof, and if there are questions, go to the ubuntu site and read the install instructions and follow them.  You should be able to install it without problems.

The only thing I would advise as a newbie is to not do a dual boot, with windows until you really have some experience.  There are many things that can go wrong with the boot loader setup and you end up with a non-booting windows.

Again, read the instructions and follow the installers defauts and automatic selections and you will most likely succeed.

I ham buddy of mine once used a plastic dog house to shelter an SGC tuner.  The tuner was one of the marine versions and so was somewhat water proof.  The dog house added shelter from storms and direct rain and snow.  It worked pretty well and the neighbors just thought he had a dog.  The wire coming from it was hard to see.

www.distrowatch.com.  Over on the left is the linux hit parade.  Start at the top most popular and work your way down.  All are downloadable for free.

Unfortunately you did not specify the windows software you want to run on your linux distro.  I assume some of the Icom control stuff you refer to is written for windows.

While you can use the WINE emulator to run a lot of well behaved windows software, it does not in general support windows programs that use windows hardware drivers very well.  You might get it to run stuff that uses the serial port but USB is so far not supported.

If you have an old copy of win95 or win98 or even win2k, you can make a virtual machine install of windows using virtualbox.  That emulated environment will run windows programs 100% including serial, USB and disk and CDROM accesses.  You can keep all the nasty windows viruses etc in a virtual pen and enjoy linux for the wrapper.

Just a note to the theoretical, you could in theory lengthen the antenna element until the real part of the impedance is 50 ohms.  Then add a series capacitor to remove the inductive part caused by lengthening the element.  However, the mechanical difficulties are not worth the effort for a 1.2 SWR.

BTW, the fact that the impedance is very near the theoretical 35 ohms means the antenna is likely very efficient.

Also I will point out that using an antenna impedance measuring device puts you miles ahead of most.  With the simple measurement, we understand the tuning, and estimated efficiency of the antenna, as well as it giving us a potential strategy for improving matching.

You can use a short stub of coax for a fixed value capacitor.  It will withstand the high voltage and you tune it by trimming its length.  Its cheap!

If you need to know the voltage withstand of the cap, you could use an antenna analyzer to set the values of the tuning components at low voltage, then measure the resulting match component values and then compute what the feed impedance must be.  Then knowing the impedance, you could calculate the voltage across the capacitor.

The computation might be a lot of work since there is reactance involved, so a lazy way might be to use a circuit simulator to set up your power level at the 50 ohm feed and see what the voltage is at the computed load with the measured components.

You could take a guess that the end fed wire gives about 5K ohms impedance and compute the peak voltage for your power level.  This would be pretty gross because the impedance at the feed varies wildly with frequency, wire length and stray capacitance.

If all this seems like a lot of work, you can just do what I do, which is sneak up on the power level and look for arcs in the matching device.  I supose if you run really high power that could be exciting.

consider replacing the 18V wall wart if it is a switching supply.  you could build an 18V linear supply that would work or modify a 24V power supply.

The R5 is not supposed to need radials.  The small ones on the antenna are supposed to do the job.  Its supposed to be like a halfwave end fed system and have very little ground current.  I won't discuss the merits of that here.

As far as vertical antennas of all types go, they actually might have a better pattern mounted near the ground.  Putting a vertical up above about about a 1/10 th of a wave length causes high angle lobes to appear.  The opposing effect is ground loss due to the ground being a lossy dielectric.  So you might consider putting it away from the house on a support just high enough to prevent people from touching it.  It will be up off the ground enough to lower the ground loss, but not high enough to be readily seen.  An added bonus would be that you wont' fall off the roof installing it.

The warning against chimmney install appears on eham every time somebody posts their idea of doing it.  You need to make your own judgement about your climate and the strength of the chimmney.

You can google the 1/2 wave end fed vertical and read about the issues associated with decoupling etc.