I am planning on building a 5x9 frame out of angle iron and was trying to figure the best way to attach the teardrop and also cover the frame without losing interior height. I want to keep the overall height at 4ft. Here is a drawing of how I was thinking to do it. The drawing shows bolts, but some of them would probably be just screws (like to fasten the floor down.)
NOTE: Drawing not to scale
Also, for all you guys that have the frame hidden, how did you treat the front and back?