Well, it's not done, but it was functional enough for a close campground tryout Friday night.
already can see that the plastic hinge isn't going to hold up to Texas Sun without "pooching" between fasteners. Will have to get me a hurricane hinge and try again.
Tracked ok with a 50lb spare car tire in the front of the cabin, but I definitely need to move the wheels back a little. Still have to trim and paint the door, and install electrical plugs for the galley/cabin, and install cabin shelving, and and and....
but it was a nice night and everyone at the campground wanted the nickle tour. Had a lot of fun.