wakeboard tower rack problem; it keeps turning! anyone had this?

Hey what's up?

So, I bought a tower rack off eBay. This rack is suppose to fit: 2" or 2.25" or 2.5inch wakeboard towers. I have a Zeroflex Tower on my 2001 X-Star... this is a 2" tower! Basically how it works is that they send you a couple different sized rubber inserts that will allow it to fit different sized racks. So with mine, I had to use the thickest rubber insert, plus the additional thin piece of rubber matting they send with it. I have attached a picture and circled the 2 pieces I had to use.

Basically, the tower holds fine until I hit some waves. The jarring of continuously hitting waves slowly makes the tower turn. I have this thing tightened prettty good but it still turns. Is this due to the fact that there are 2 rubber inserts being used? Anyone else had this problem?