Did you fix this with a helicoil or a tap? I just did the same ^%#$@ing thing, except the bolt is the one that also holds on the brake light switch, and I could use some clarity around what size helicoil and/or tap to get.
I find these stripped on about every 5th or 6th engine we build. I use a 6mm x 1.0 helicoil which works great. I think the proper bit size is 1/4" to drill the old hole out to, then use the helicoil tap (comes with the small kit) and then install the repair coil. Takes about 3 minutes with the cover off and out of the way.