Hello Alaskabear, ninty-nine thousand, six hundred and eighty seven. I wonder if that number has anything to do with how many bears are left up there. Looks like you figured out exactly what you plan to do and how it will look when you get finished. Well more or less, lets see, what to cover it with, final shape, design of galley and shape of fenders. It'll all fal together as you go along.
I bullt an 8 footer on a 6ft frame, no problems so far, and don't expect any. You might want to consider altering the front and rear overhang, so your axle will be in the right place in order to attain the proper tongue weight. I had to shift mine even after I bolted the floor to the frame.
As problem questions arise, be sure to ask them here on the forum. We have lots of folks with lots of answers. Welcome aboard, take pics, post 'em and oh yes... good luck on your build.

Roly