I don't think I would trust my knees and ankles to jb-welded foam. I would say that your safest bet (other than replacing the board) would be to t-nut the insert. This will cosmetically be the most ugly way to do it, but should structurally be the best. Drill a hole thorugh the board, and install one of these bad boys from the bottom up:
I haven't ever done it myself, but have heard of others doing it, and having it work flawlessly. Won't be pretty (from the bottom) but should do the trick. Good luck!
-Steve