Hey, i don't have any great solutions, but I do have a word of warning about the treated plywood mentioned in one of the other solutions. The new treated lumber contain a chemical that is exrtemely corrosive to aluminum! DO NOT use material treated with CBA, ACQ2, Natural Select (and a few others I don't remember right now!) in contact with aluminum. Consult with whoever you buy your material from to see if it will disolve your boat! I don't mean to be so negative, I would just hate for you to do more damage trying to make the repair! (I am an estimater and salesman at lumber yard in Michigan, and have seen many problems with this in reguard to building materials, but it applies to boats as well) If you can find it, CCA treated lumber is o.k. to use in contact with aluminum. Is there any way to have a welding shop heli-arc (welding for aluminum) nuts to the bottom side of the deck, and then bolt the bracket down using them?