You could fill the holes with araldite or epoxy resin then re-drill them and tap em out hmmmm its alot of effort or just go and buy some new ones usually about $60 for a set of four from what i've seen
Cheers I was thinking it would be to much effort it fix but they practically new so might just keep the other three for spares and see if I can be bothered with the effort to fox the other one.
" recoils" or " helicoils" are thread repair inserts not cheap for a kit around $50 for 10 I think, available at automotive shops. You will need to be reasonably handy to repair aswell.
Easier buying a new fin, unless your wrecking loads.
