My thought was to shim the rings on both sides. Since 1mm is about .039" I could use a .020 shim on both sides to take up the 1/2 of 1mm per side and that should keep the ring on center with the front one. Once I make the shims I figure one of the heavy duty epoxies will work to hold them in place or if I get adventuresome I can solder them in place. In either case they would be premanent. Thanks for the thoughts though.