1968 Sea King 14'

I am in the process of adding a casting deck to my 14' boat (1968 Sea King). I want a deck that is 3" below the top of the boat. I am thinking of using an aluminum angle of some kind every two feet, starting at th transom, and every 2' until i near the bow, have another one. then, i will run a 2x4 accross the width parallel to the transom. A total of 7 beams and 17 angles. The horizontal beams will be supported by vertical 2x4s notched out to the boats ribs. Will the aluminum on the sides of the hull be too thin for the Screws to support the angles and casting deck? Think of a piece of paper, stabbed by a pencil and ripping the pencil through the paper. That is what i want to avoid. Ripping the boat hull with rivets and screws because the aluminum is too thin.

I am planning on doing a similar project on my 12' Starcraft. I will be putting 2x4's on the ground as a base, then use that as support for a casting deck, however due to the size of the boat, the deck will only be 6' long. Remember, when doing a casting deck, never use the pressure treated ply despite the tempting price. Good luck, I'll be following this project!