I couldn't agree with ya more George on pretty much every point. It a nightmare trying to find a frame that is usable for these classes, and once you do find one, it takes a ridiculous amount of time and money to get that frame to a state that is raceable. Just like Bob said, pretty much every FXT or supermod out there is built on a custom frame and disguised as mower frame and like you said, there is no real competitive advantage to it. I get the whole sticking to the roots of the sport by staying with a mower frame, but honestly by the time the they are finished, the "stock" frame has nothing to do with them resembling a mower because you cant see the frame.
I have also always wondered why the original F/X class was allowed a custom frame but the new "top tier" classes arent