Has anyone tried to build a stitch and glue from fibreglass sheet?

The reason I ask is that we have a marathon race early september for which my pioneer was lacking in the speed department for the distance (30kt miles) last year. I was thinking about maybe making a night heron for this years race but time is against me now.

Would there be any disadvantages or problems with starting out with fibregalss sheeting instead of plywood? then reinforce it with an internal layer of fibreglass?

I am lucky enough to be in the position of having fibreglass sheeting of any dimension I like (within reason) at hand from the family business so the material isnt a problem, more the build issues I am not too sure about!

Cheers in advance

Alan