I remove all my Handi/Ultra rails, clean the holes down to bright metal, lap the rail to the barrel with a piece of fine crockus cloth layed on the barrel, then bed it in blue loctite. I don't leave any questions as to whether the rail was mounted properly or not, then I know for sure if there is an accuracy problem, it's not a mounting issue. Lapping the rail is covered in the FAQ in Perklo's Superlight post.