Question: Does the fiberglass give the boards a faster REFLEX? That is to say, does the glass not only stiffen the board, but upon flexing the board when turning, does it make the board more QUICKLY SNAP BACK to its original unstressed shape?
compared with plywood, i would say adding glass will give you faster reflex (higher natural frequency)
on a simple level , a board is a spring with a mass .
the stiffer the spring, the quicker the natural frequency (reflex)
the greater the mass, the slower the reflex.
adding minimal glass to top and bottom surfaces would easily increase the stiffness more than the weight ( compared to plywood)
other things to consider for better stiffness/weight (reflex for you)
length of board
thickness of board
thickness profile (where does board actrually bend )
concave vs flat
laminated planks vs plywood ( all the grain is going lengthwise)
lighter wood (cedar, pine, pawlonia, balsa)
you get the idea.