Sounds like you really want/need a '736 or some other 6 Meter capable radio.  Why not look for a '736 or an IC-756Pro, or Pro2.  Any would likely be cheaper than the '737, plus the time and materials to make it something which it isn't--a '736.

Will the trees have any effect on HF?  Probably.

Will it be significant?  Probably not . . . unless the tree and antenna are in parallel contact or closely coupled, within a couple of feet.  You might notice a change in SWR on wet days in this case. 

Rather than a setting up a vertical, you might utilize the trees for supports for a dipole or loop.

Remember, any antenna is better than no antenna.   So, try it and have fun!

A NE sloper is a clue to me that you're looking for European DX.  If so, go with the half-wave sloper, BUT fold the lower half (below the feedpoint) back toward the support structure--think of an inverted-V rotated 90 degrees so that the apex is pointed in the desired direction.  This configuration tends to favor signals arriving at a low angle.  73.

I should have added, in my initial posting, that I did the usual Google search, then did some second level searches (i.e. for indices for QST, NCJ, etc., then searched those.)

I found only 1 article so far, in Sep/Oct 1997 NCJ.

I had a Corsair II and received excellent audio report when I used it with a Shure 444D.  It is a very versatile microphone with a lot of punch.  A friend who lives about 15 miles from me said that, even at S1 signal strength I sounded like I was 7 feet tall.

The 444D is no longer manufactured but I see them occasionally at hamfests and here on e-Ham.

Over the years I remember seeing several articles in amateur radio magazines on rebuilding aluminum Yagi antennas. (i.e., dis-assembling, cleaning, re-assembly, and trap repair).  Now that I need this information, I cannot find it.  Can anyone provide a reference (publication, issue, page) for any article on this subject? 

Two suggestions:
1. Listen to ARRL Official Bulletins in CW; they're sent at 18 WPM for about 1/2 hour.  Just listen as you would listen to a news broadcast on the AM radio, don't try to copy on paper.  After a while certain common words will start to register in your mind: and, the, of, radio, with, etc.

2.  Listen to some contests in CW.  You'll encounter "Run" stations which sit on one frequency and call CQ.  Copy what a run station sends, on paper if you have to, but continue to listen to that station after you know his call and exchange.  You'll get his rhythm and eventually you'll begin to copy the stations answering him. 

Thinking back to my early days in Amateur Radio, I shared many of your thoughts about high equipment costs when I looked through the advertising pages of QST in the local library.  (Couldn't afford an ARRL membership then.)  Fortunately, some local amateurs clued me into the bargains of used gear and the generous fraternity of Amateur Radio.

My first station consisted of a borrowed transmitter and an old receiver, purchased from a local ham with money I earned cutting lawns and delivering newspapers. 

It wasn't elegant, but it worked and I had FUN.  As a Novice I worked 37 states and 3 countries for a total investment of under $50, including crystals and antenna.

There is a LOT of very functional older gear in ham basements, attics and garages.  Some is available very cheaply.  Many clubs have "loaner" rigs for new members.  Look around, and ask around--you'll be amazed how inexpensive a functional station can be.  And, a $250 used radio will give far better performance than a $250 brand new radio ever could.
 

I've had very good luck with SAFCO lighter plugs when they were easily found in auto parts stores.  Now, it seems that auto parts stores don't carry lighter plugs of any brand anymore.

Are there any brands available from Mouser and Digikey which you can recommend from personal experience?

I used a similar antenna for several years.  Rather than using a wooden mast, my antenna was hung from a high tree branch with clear area below.  It played well on 20 & 15, but rather poorly on 10 (at a time when 10 meters enjoyed decent propagation).  I fed the antenna with window line and matched it to my transmitter with a Johnson matchbox.

I didn't do any computer analysis of the antenna, but used it in several DX contests.  It was an adequate performer, putting about 80 countries in my log on both 20 and 15 with a 50 watt transmitter in a casual effort.

The antenna occupied a fair bit of my garden as the radials were really two, low 20 meter dipoles at a height which was neck high for an adult.  I'd put it up in the fall, then take it down in the spring to avoid strangling myself when cutting the lawn.

If I had your 30' mast, I'd be inclined to try a 30' dipole, bringing the ladder line away from the mast at right angle for a quarter to half wavelength at 20 meters.  Using ladder-line and a link-coupled tuner. I wouldn't be concerned about the "missing" 3'.  I would try to keep the antenna a few inches from the wooden mast.

Yes.  The company was unable to identify any retail resellers.  They specifically noted that Digi-Key and Mouser DO NOT carry their products.  No SAFCO products appear on the Allied Electronics web-page either.

SAFCO is willing to sell to me directly but with a minimum order quantity of multiple hundreds.

I'm looking for a (retail quantity) source for SAFCO #210 fused lighter plugs.

Years ago I had a set up just as you describe.  (15' above ground, then radials).

I found that a 105' long end fed wire (through a tuner, of course) with the 15' long wire connected to the tuner's ground terminal was quite an effective antenna on 80, 40 & 20 meters.  I worked about 200 countries with that simple antenna while running 50 watts.  The antenna tuned easily on 80 & 20, but I sometimes had RF feedback problems on 40 which I tamed with the addition of a counterpoise attached to the ground terminal of the tuner.  

After thinking about it, it appears the antenna was an OCD (off-center dipole) in an L-configuration.

Probably yes.  Any close-by structure or plant material has the potential to absorb radiated RF and attenuate received signals.  Did you ever drive under a branch bank or gas station canopy and hear the signal strength (broadcast radio or ham band) fall off?

That being said, any antenna is better than no antenna, and RF has to go someplace.  If 5' from the house is THE BEST you can do, the antenna is or can be made resonant, and you're not causing unacceptable RFI or hazards to people--go for it.

If you don't have it, the datasheet for this microphone is available at:

http://www.shure.com/stellent/groups/public/@gms_gmi_web_ug/documents/web_resource/us_pro_444d_ug.pdf