Jon
We talked about the alum tubes in the sponson and carbon thur the tube then drill the mounting holes thur the carbon tubes and tap the alum for small screws. Not alum tubes all the way thur the tube.A little misunderstanding there.The sponsons are a little heavy for the 20 boat and they could be a little smaller.
Dave Roach
OK, I understand. I use CF tube in the sponsons I build and add a 3/4'~1" gap between the sponson and main boom tube. THis space give a place for the stub to shear if I hit a bouy or other hard object. If you tap into the aluminum stubs, it should work fine. In any event, nylon washers should be placed under the head of the screws to protect the tube.
I agree that the sponsons are big and heavy; but they are what Aeromarine produced when they made the boat. I prefer sheeted foam sponsons for strength/weight ratio. In fact I have both a 20 and 90 hydro mold sets that include sponsons, that I will never use because of the weight issue. These molds are from the 80's and the sponsons are huge (and blocky).