I have had some part sheets of plywood and epoxy hanging around for a while and have just enough to add a tank with hatch at the bow and then with what remains something in the stern. 

Then going to add a down/reaching sail. No board just a paddle and posible a skeg. Still thinking about the sail, keep going between:

• simple battened triangle 
• stand lug with boom
• standing lug no boom
• balanced lug 

Anyway simplicity the goal so letting it percolate