[vin63]

I didn't box my frame for vertical load bearing, but to resist some torsional flex/movement. I transferred my plate patterns to a water jet mill and cutting the patterns from 0.1875 1018 steel plate. The plates fit snuggly inside the C-channel frame (which is not heat treated) and I TIG welded them in an inch at a time rotating locations (both front to back and top and bottom). This, in addition to the strength of the OE sheetmetal structures helped to reduce some of the torsional flex in my case without having to go the full roll cage route.