Why wouldn't one put gaskets under striker pneumatics if it makes
them easier to remove, and to achieve a perfect seal?  However, as
has been said, the gasket material needs to be strong enough not to
delaminate, and so is unlikely to compensate for any unevenness in
the boards.

Those masochists who wish to can try to use hot glue, clamps, etc.,
but I've encountered too many expertly rebuilt stacks with leaks
between the boards.

So I'll carry on priming decks and striker boards with water-soluble
PVA solution and (when dry) sticking them together perfectly with RTV
silicone adhesive.  It's its own gasket, a perfect seal every time,
very strong, easy to remove pneumatics and adhesive, and absolutely
no harm to any parts.  Meets all the requirements.  Nothing better!

Patrick Handscombe
Wivenhoe, Essex, UK