I've had my Tango Down vertical grip on my Surefire rail for a while now, but I was never really happy with the fit (probably the rail's fault).   Sure it locked up tight fore and aft, but there was always a little bit of side to side play that bugged me.  I realized that there was a little bit of space between the flat spots on the grip and the actual rail.  The plastic was not making complete contact with the metal.

My solution was to apply a thin layer of JB weld to the flats on the grip thus building them up.  I let it sit over night and then did a little fitting with a small file.  Now it still slides on and off easily, but it also locks up tight without the wobble.  I hope someone finds this usefull.  

Good tip. Thank's for sharing.