: the build had slowed to a virtual stand
: still and the deck spread by about 11/4" (1-1/4" ?) amidships.

When one surface of a wood strip panel (your deck) is glassed, that surface is
essentially frozen, and the wood can no longer expand and contract with the moisture
content of the air.

The other surface (the inside of your deck) will continue to expand (more moisture)
or contract (less moisture) with the content of moisture in the air.

The best course, is to wet down a wood surface that has shrunk due to dry air, or
to dry an expanded surface that has too much moisture, relative to the "frozen"
glassed surface.

If you force a surface into place with mechanical means and then glass that surface
you have entrapped the stress you created and it may release later weakening or
damaging the glass lay-up.

Even though you have added a seal coat of epoxy to the bare wood you can still remove the
excess moisture that has expanded the deck by applying a heat source, like heaters or the sun.

All the best,
Rob