Get some short Allen-head bolts, and eliminate the problem altogether. Most hardware stores, or places like Home Depot should have a good assortment of them. Take a Dremel tool with a cutoff blade and shorten the Allen wrench if necessary to get access to the bolt heads. I used to do that on smallblock Chevy header bolts before I figured out headers aren't worth the hassle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!