Looking at the picture, can you tighten the clamp up so that thinks do not rotate?...maybe then measure the gap and make a spacer to fill the gap? The 1 1/2" bar seems to be the problem...I didn't have the issue with the 1 1/4".

One other suggestion is to change out the controls and switches like: http://www.jokermachine.com/onlinecatalogstreet2004.asp?CategoryID=64