I would say go ahead and repair the hole where the gas tank is. Since you've got the plane apart, now is as good of a time it will ever get. I had a VMAR stick that had holes in the wood under the fuel tank. I flew it and flew it with no problems. I gave it to my dad and he resheeted the whole plane. Funny thing. It's a lot better looking plane now than it was, and to pick it up feels a lot sturdier in your hand, but it still flies exactly as it did before.