Hey John. Sorry, I didn't know that all NT stores do not carry the same inventory. Is it a State Regulation Thing? Seems they could order the thing for there next trailer delivery if the handle the Carry-On Line.
You are right about the floor being cantilevered over the sides over the sides of the frame. About 8" on each side. The framing under is ripped 2x4 to support the floor to the top of the 2x2 angle iron of the frame. The sides and floor are framed together with 1x2.
This is a shot of the side wall to floor frame in the porta-potty closet. Sloppy Painter!
I seem to remember this being discussed before, be it some time ago. Since the cantilever is so small and the chance of standing weight on the edges of the floor is minimal, all works well.
This size and style of Camper has been built on a 4x8 Harbor Freight 8" wheels Trailer with 12" (or more!) overhang and no under floor support. In fact it was the original "Puffin" by Steve Wolverton! (Thanks Steve, your middle name must be TTT!)
Now, having said all that, my last trailer was a 10' long standie with insulated walls and aluminum clad. On that 5x8 nf I did add "outriggers" to carry the weight outside the frame. I believe that was overkill. Page 10 of my album has pics of that trailer prep.
So what ever you decide, Good Luck with your build and Take Lots Of Pictures!
Gary