Don't know if this will help anyone at all but I've been changing fins a lot recently in futures fin boxes and after my last surf I found one of my side fins was super loose. When I tried to tighten the screw it just turned and turned and never tightened. Great. Stripped the tapping in the box. Ugh.
I saw some solutions which involved 5min epoxy, a drill, new tapping, etc which all sounded a bit more time consuming than i was willing to commit to off the bat.
I very carefully removed the screw, cleaned the inside and around the box, squished some foam into the box where the screw would settle into the fin, squeezed super glue into the top of the screw hole, waited to dry, removed the squished foam, popped the fin in, carefully screwd the screw back in using the "good" tapping at the top end of the hole and, bam, good as. At least for now.
I'll see how it goes but essentially it was just some super glue in the hole that gave a fix.
Hope it helps.
