Hey,
had some trouble with the reef last time I was out and managed to lose a fin. When it came out it took the little peg of the fin box (futures) with it. The fin box is alright except for the little peg thingy, so basically I can put a fin in there, screw it in but it doesnt have anything to latch on to in the back end.
Can you somehow repair this or would you need to replace the whole finbox?

She's knackered. Notch it up as "Lessons in why I should use twin tabs 101"

Never had one break, but this is what I would try.
1. Replace the tab with a piece of 316 stainless rod. So first find some rod or file down the threads and cut off the head on a SS screw or bolt.
2. Get an L shaped piece of wire. Heat it up and melt holes in the plastic box where the tab was so that the SS rod can be fitted in place of the tab.
3. Use a syringe to inject resin through the holes into the foam and resin behind the fin box.
4. Insert the replacement SS rod
5. Clean up the resin that flowed into the box once it has jelled.
6. Hope the resin has sealed the box so no water seeps into the foam.

And be sure to use epoxy resin if the board is EPS.
Let us know if it works.

Sounds like a good excuse to buy a new board to me

Totally agree with Andy, get a new board or two just in case it happens again.

Have you thought about glassing your fins in permanently?

Or you could superglue in a replacement.

Could you drill and tap the back of the box same as the front .Probably need a longer screw.