Too late now- but you should always sheath the outside of the boat with a layer of cloth and epoxy.
Put it upside down on sawhorses. Make a ridgepole out of 1x3 cheapo spruce strapping so the tarp does not sit on the flat bottom. Finally, wrap the boat but don't seal the bottom (some bungee going from side to side under the skiff will do).
The idea is to allow for some air flow. As the boat is not sealed with resin, you have to allow the surface to breathe a bit. Yes, making the frame will be more of a PITA- but it's the price you'll need to pay.
