The deck seams aren't that bad, they're split on the actual deck seams of the real ship.
I would suggest assembling the deck on a flat surface, inverted, to make sure the seams are as tight as possible. Once dry, flip it over, tape off as close as you can get to the seam on either side, fill carefully, then wet sand carefully. Once it's to your liking, remove the masking tape. Re-scribe any small details you may have obliterated while sanding.
Jeff