I have always preferred bolts and lock nuts, but recently had to tap a mount because the bottom could not be reached to add nuts.

Now, I've done this before, numerous times, and never had a problem. But this time after one flight, I started my engine for a second flight and saw a washer under the head of a mounting bolt "rattling".

I grabbed my hex wrench only to find the threads stripped. I checked and found another one of the holes with stripped threads.

I'm not sure if the mount's material was defective or what, but I'd never had one strip out before, let alone two. (I pulled the mount and set blind nuts into the bottom of the new one. )
Dennis-