bending characteristic is mostly more important than pure theoretical thinking about the wing profile. most wingmast sections mostly have the problematic tendency still to be to hard fore aft and to soft sideways (compared to soft aft). I know that in the A class those guys who builded the first holland composites spars (the mould later went to austria and became fibrefoam) believe you nowadays could just use a tube profile with a thinner diameter than current A-class mast profiles and glue a sailtrack on the back of it. the aerodynamic issues could be solved within the sail for example like the windsurfers do...
but main topic than would be to get the sail right!
but you can always easily change the bending characteristic of such a tube-carbonmast by simply adding unidirectional carbon fibre strips to it...

if you go the other way (for example with a core of styrofoam) you actually will have very little control what the final bending characteristic will be like and chances to get it right are quite low...

for reusing an prefabricated carbon tube, you might not even need an autoclave...