pic: 6WD Riveted Frame Development

[s_forbes]

Originally Posted by M. Mellott

I took a look at the pictures and noticed you notched the U-channel to insert the end into the end rail similar to this design. However, there appeared to be nothing joining the four fiberglass frame members together except for the bellypan and the four sheetmetal gusset plates on top of the four corners, with nothing actually inside the corners. Is that correct?

Correct. It was plenty strong enough with just attachments on the top and bottom, any more brackets would have been unnecessary and too much work to put in. Thin aluminum channel may require more bracing if it's constructed in the same way, but the fiberglass is nice and stiff.