Steve, Roger's totally right on the threadlock, it has saved the day on more than one occasion, but if you're big or powerful or gonna change it often or just plain go hard on it, for the stripped epoxy TT thread get some brass threaded fin inserts (old fin or local dealer's old fins if you can't find these easily).
Drill down (drilling out) the threaded (stripped) tapped threads to oversize the hole, then carefully drill sideways thru the TT head to insert the brass thread inserts. There's a few pointers to be aware of, most notably accurate setup and square 90' drilling (use a workshop drill press, esp for the sideways insert hole/s. And overdrill (not toooo much) the depth of the bolt holes by a few mm deeper than the bottom of the insert holes ; this allows the fin bolts to screw thryu the insert and out the other side- at least a little_ before they start to impact into the base material, at which point extra tension starts to pull the insert right thru the top of the base material and
Sounds complex, with the inserts in one hand and the drill press in front of you, it's a no brainer and brings an otherwise good fin back to full and reliable long term service.
Cheers ~ Ian