Hey rolf, I think you'll find the mentality thing is like we enjoy doing stuff the hardest way possible for the least possible return on effort! But hey I've never owned a playstation so time needs to be spent somehow.

My 15m stick (actually I sold the boat recently so its no longer mine), was supposed to be on par weight wise with an alu section of the same size, strength however is better due to the correct fibre orientation for the expected loads. The carbon version would have been approx 30% lighter again. The mast never actually got weighed so actual figures I can't give.

Regarding a f16 size mast, I'd still lean toward a base of ply and I'm only talking 1.5 - 2mm, just enough so that when bent to the desired curve it'll hold the shape while adding the carbon. As for fibres in the wrong direction, you'll still need some fibres across the grain to hold it all together, the large mast had 20% of the uni cloth running at 45 deg to the axis for resisting torsion, I'd suggest a 0.5mm layer of ply at 90 deg will add very small weight and big time in helping hold a good shape, tapering also would be easy enough, prebend maybe a little troublesome but thin ply will compound curve to some extent. Still its your mast and I'll be happy to see how the dissapearing foam trick works if you do that.

The only other main concern I'd have is that the mast will not be predictable enough to get a guaranteed sail that works with it. Maybe the first sail will need to be experimental to see how it handles the loads.

Good Luck
Phil