Blizz-
Thanks for the response. Sorry about the other thread, I am new at online forums and am not familiar with the etiquette on hijacking a thread. Now I know.
I don't remember seeing that side view on your frame when looking through your build, I think most of the pics were close up inside the building. I did not realize those side plates went that far up under the cab. Bolting the cab solid to the frame makes perfect sense, sometimes I think too hard and ignore the obvious. I could easily eliminate the rubber mounts and fab some brackets to bolt the cab solid to the frame. Also ignoring the obvious, I should have taken a cue frame class c motorhomes there instead of just the toterhomes I've been getting ideas from. The only factory toter I've come across with a roof cutout was the Pony Xpress, but that's a lighter duty unit on a 5500 chassis with only an 8' box so they probably don't get much chassis flex.
http://www.hgrstrailer.com/pdf/pony_.../toterhome.pdf
I can't imagine those rubber mounts do much for ride quality anyway, but my truck does have leaf springs and not the luxury of your air ride. Maybe I'll need to scrounge up a a pair of air ride seats at the local truck junkyard.
Thanks again for the help!
Dave