Yes, it will work.  But don't remove anything from the bottom, remove the top section of aluminum above the 30 meter trap to shorten the antenna.  You will lose 40 meters.  However, you can restore 40 by running a wire from the 30 meter trap horizontally to make up for the removed section.  Make the wire approximately the same length.  You might have to play with the various sections to get swr down on the individual bands or maybe your antenna tuner will do just fine with it the way it is.  Good luck and have fun experimenting.  That's what the hobby is all about.

70 cm would be my easy choice.  Since you are in a built up area, there will be far less noise on 70 cm than on 2 mtrs.  Plus, the usual advangates...more gain on a dual band antenna, less activity (typically) on the band, etc.

Congratulations to all who heard your QRP signals.  Receiving weak QRP signals requires a great deal of skill, as well as low noise, sensitive, and selective receivers.

I have the Larsen 2/70 NMO.  Best antenna I've come across for my dual band mobile in over 3 decades of hamming.  Professionally built, solid, durable, excellent performance.  I highly recommend it.

I will mention that my Hy-Gain TH2MK3 two element tribander works quite well with a low swr and some gain on six meters.  I've been using it on six for over two years now.  No modifications, just a standard TH2.

I agree with K5LXP.  Leave it circular.  The 3 db penalty is more than offset by the fact that you can work stations vertically, horizontally, and the satellites if you wish.  I've run a CP antenna and found the 3db to be a non-issue.  A friend of mine has the same antenna up now and finds the same good results that I did.

Check out the "unofficial" FT847 home page at
www.en.com/users/rayd/ft-847/

You will find out more about your 847 than you ever thought possible.

I have used a low, 160 meter full wave horiz. loop in the past.  I recommend using ladder or window line (300 ohm or 450 ohm) if possible to a tuner.  You will find that it is a killer antenna on the higher bands.  Of course on 160, radiation tends to be straight up and will do a very good job in your region, but not the best for dx. As you move up in frequency, the radiation angle starts dropping and the antenna will be a good dx performer.  BTW, right now, I have a full wave 80 meter loop up at 30 feet or so and get good results on all bands from 80-10.  Mine is fed with ladder line.
Hope this info helps.

Six Meter Low Power?  How about this....Sunday morning I was handing out points to the field day crowds...on six meters.  It was wide open from Northwest Indiana first to Florida, then progressively west through Mississippi, Alabama, Louisiana, Texas, then New Mexico and Colorado.  I worked about 50 - 60 stations in all.  Guess what...all with 2 watts output to a five element beam!  Also switched to 52.525 FM and worked a bunch more with 10 watts out to the same antenna.  Low power on six works just fine.  You just gotta be there when the band opens.  That means checking out the band frequently for band openings!