Use shouldered Allen bolts and ream the holes for a fit that's just shy of being pressed into place. Just drilling the holes oversize to get them round won't be rigid enough to prevent them from wobbling out again. Hot-set rivets would be the best fix.
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!