I have not gotten one off yet...so the current question is, how do you get off a stripped allen head screw?
Use the same size drill bit as the threaded portion of the screw (drill needs to be smaller than the head) and drill the head off. Go slowly. If you have one or access to one use a left handed drill bit and you may get lucky and it will back the screw out. If red locktite has been used you will have to apply some heat to soften the locktite.