That is what I have.
is any oner elsew having this problem? How do you gys mount you unions to a channel board? Also what is C3? and what would padding do to help? Could I just get a power drill and drill them tight tight?
This is just what happens when you only have 2 screws holding a binding on. The only thing you could possibly do is place something abrasive between the binding and the board to limit it's ability to slide.