I would think the floorpan would be the weak link in the 'vert. If I recall correctly, MWS made a huge X brace for his (or customers?) 'vert on the underside of the floorpan to increase rigidity.
Later
"Only two things are infinite, the universe and human stupidity, and I'm not sure about the universe." -Albert Einstein
When was the last time you *really* did something with your Z to call yourself a Z enthusiast?