There was a topic about this on 24hr campfire...sounded like guys there use JB Weld to bed their mounts. This is what they had to say...
Clean all parts up with brake clean including the screw holes on the receiver. Put a thin layer of JB Weld on the bases and on the screws, then install. Use a Q-tip with rubbing alcohol on it to clean up any JB Weld that comes out along the edges as you tighten the bases down.
Use heat to remove if ever needed.