I can't help but think of all of the semi-trucks that have c-channel frames that carry 80,000 lbs. Their frames are designed to flex to keep them from breaking. I can see why somebody building a hotrod would want to super stiff frame, but if you are building the truck to haul loads, I think some flex in the frame would be good.

Never hold your farts in. They travel up your spine and into your brain...that is where crappy ideas come from.