I have put together a few boards and have never used wood ,because of weight.
Fiberglas supply in Bingen Washington can get foam to you quickly
it's very easy to work with
if you vacumn bag it is a very time consuming and expensive process that you can't tell what's going on after it's layed up
I've had good luck and bad with saturation during vacuum bagging.
so until I'm ready to produce boards in multiples where I can regulate the amount of resin needed for each board ,I will stick to hand lay up where I see what going on .
concaves are just more shaping
not much help ,but it's what I do