I got the 12 inch model.
I did cut the frame as recommended and axle.
I did extend the tongue as recommended.
Made my own cooler bracket.
Sears Top.
Been cross country and all over AZ pulling it.
Tracks great, hardly know its there even when full.
Not as fancy as the others but just as functional. And you made.
I did the Northern Tool, which basically has similiar trailers. I opted for the 8 inch tire. I think 8 inch or 12 inch is a personal choice. The biggest thing I heard about 8 inch was that they spin too fast? Having 12 inch tires means less rotation per miles covered. I have never had a problem with my 8 inch.
On my wing, the 8 inch sits the tongue and trailer about level when connected, maybe a slight downward tilt at the tongue. If the hitch ball was taller, I'd have done the 12 inch, just for the height so that the weight would angle down on the hitch ball, not up and back. 8 inch works fine on the wing.
I didn't cut mine down, but did extend the tongue. Primed and painted it black, put black diamond plate (aluminum) down for a floor, then mounted a black truck tool box, 24 inches wide, 48 long, on the trailer. Only about 11 cubic feet, but my design was to have 8-10 inches down each side to strap on water containers, gas, tents, chairs, whatever, for camping. With the inside storage for clothing, foods, etc.
Good luck. It's time consuming, but you fell good afterwards knowing you built it.
Join this site for lots of info and ideas.
http://forums.delphiforums.com/MCTrailertowing/start