Really outstanding build, thanks for documenting it here for us!
I read all 15 pages and didn't find one item -- how did you tie the tent frame supports to the tub? I thought maybe you went through the tub and tied into the frame, but then saw on a later page where you pulled the tub and extended the tongue, so didn't appear it was welded through the tub.
I am planning a similar build with a Bantam T3C and my wife has requested to be able to get at the gear without leaving the tent vestibule, so a lift-top design is out. A frame like you've built will satisfy that, I'm thinking maybe canvas sides on the frame as well to help keep dust and dirt out of the trailer. Or a tonneau cover like you built.
Thanks again!!