You will be fine with either a larger bolt or helicoil, the early Stealths had an Ali block imbedded in the back of the layup and the later ones had a Delron ( or something similar ). Most people forget to put some sort of grease on bolts and eventually corrosion between dis-similar metals locks the threads.

John Pierce the maker of the Stealths is still about, have you tried contacting him ?