I will probably get comments on this but, I only mounted the rear exchanger using the rear mounting holes. and I used stainless steel screws, that way I could take it off if I wanted to (don't know why I would ever want to). The screws are smooth and rounded on top and take a allen wrench. I get NO noise or movement with this installation.
However I did take it off or loosened it last night to install a loop to hook my trunk bag to. So I guess it was a smart idea.