The fore and aft decks are 48" wide, but their depth can vary according to how you build. Get the depth from the frame that you have made and cut them.

If you used 1/4 or 5.2mm ply for the bottom, you'll want skids to stiffen it up - laminated skids are easy to make and attach. I'd recommend 5 skids for this boat, but that is just me.

Shape and attachment of the leeboard and rudder is up to you. The best shape I know of I learned from Micheal Storer and Peter Hyndman: Oz PDR Foils