Here's my design... went overkill and used 1/4 wall thickness (actually .22) for tighter tolerances.

http://s5.photobucket.com/user/rmccartney/library/Rotisserie%20Fabrication?sort=6&page=1


Inside welds were ground down using a cutoff wheel in this modified tool, 1/4 rod welded to 1/4 shank arbor:


http://i5.photobucket.com/albums/y167/rmccartney/Rotisserie%20Fabrication/225a74ce.jpg


http://i5.photobucket.com/albums/y167/rmccartney/Rotisserie%20Fabrication/42c22666.jpg


I'd say this would hold anything you want to put on it... The adjustable CG allows you to set up for perfect balance. I can rotate it with the car installed with one finger, and it stays where it stopped.