I just bought a boat where someone did exactly that. It wore through the aluminum can and the hulls were sloppy again. What I did to fix it is kind of an extreme fix. I've heard of people doing it on other boards, but the boat is rigid as hell!

1) Take the frame completely apart. (Including drilling rivets)
2) With some 80 grit sandpaper, skuff the aluminum frame pieces where they fit together.
3) Apply a thin coat of epoxy to all of the joints
4) Mix a batch of dense filler and epoxy and coat the joints liberally
5) Reassemble the boat including new rivets
6) MAKE SURE to measure diagonals so the boat is square and either place it on a jig or measure bow to ground and stern to ground distance to make sure the hulls are parallel in all directions.
7) Once square, pull the rivets and tighten the bolts.
8) Measure again and adjust if necessary.

I'm telling you, it's worth it. If you absolutely must take the frame apart someday, heat the aluminum knuckles gently until the epoxy melts out. But, I don't ever plan on taking mine apart.

Like I said, extreme, but my boat cost me $300, so I figured what the hell. HUGE improvement.