Karl, how about using a rounded-head carriage bolt as a through bolt, and grind the rounded section flat on top a little if necessary for more clearance? You can either slot the top of the bolt for a big screwdriver, or figure out a way to file the top hole into a square to accommodate the carriage bolt head.
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!