hi there
For the fear of typing another invisible posting - here goes
As far as fibreglassing and sealing the internals of the inside of a wooden hull - personally - I would say go ahead and do it
for the simple reason - bare wood, even painted wood - when wet, will expand and where you have one side of the timber sealed with your Epoxy Resin and the other side of your timber free to move and expand, it will split away from the Epoxy Resin as it expands and also split at the joints. The is because there is nowhere else for the wood to expand evenly - if therefore you seal the hull with Epoxy or Fibreglass Resin it will prevent any water penetration and therefore eliminate the chance of expansion.
The only things is, one has to double check and ensure that
every bit of planking that is visible inside the hull is well sealed. The other thing is polyester resin is NOT 100% waterproof.
Epoxy is the better option for sealing.
I also have done this to life-sized wooden hull to seal them, using the West System of Epoxies and I do have some models which I did about 30-35 year ago - and they are still going strong.
John the invisible