I've read many times about sealing the balsa before laying down the polycrylic to prevent absorption.
I'm thinking out loud here as I've never used poly and fabric. HEY, no smart remarks from the peanut gallery
How about spraying a mist coat of the polycrylic on first to seal the wood? It could go on pretty dry if you just "dust" it on. On the other hand if you put the poly directly on, most of it will evaporate.... right???? so not much weight to be gained anyway????? I have also read some will "seal" the wood before using epoxy. It seams a bit counter productive to seal the surface instead of letting the bonding agent (epoxy or poly) not soak in a bit for the best bond.
So with he above said.... If you chose to seal the wood to prevent absorption, I would find a way to use the same product to seal, as what will be used to bond the fabric of choice to the wood. I think you will solve any issues from dissimilar materials bonding (or not) to each other.
IMO, you have only one chance to bond the fabric to the wood as securely as possible to gain the most strength and that is the first coat of what ever product that touches the wood and cloth at the same time with nothing between them.
OK... My flame suit is on
Ken