I've boxed a lot of frames for round track racing, particularly dirt trackers. The frame has to be rigid enough to take suspension load adjustments without flexing excessively for changing handling. Of course, the roll cage adds a lot of rigidity to those frames, in addition to the box structure. Instead of completely enclosing the open section of the frame, I prefer to cut big elliptical holes in the boxing plates. It makes it much easier to run fuel lines, brake lines, and wiring that way. and any or all those things are easier to replace when necessary. The holes also keep the weight down somewhat.
Jerry
