Making mistakes is part of the building (at least part of my building) and as you may have noticed I decided to show them even though some are a bit embarassing. I hope others will benefit from it.
When I made the hatch coaming I figured it would be best to start it at the beginning of the deck-main bulkhead radius:
Then I realised the aft side of the hatch will slide on the coaming and drop down at the end of the coaming. The coaming should thus be extended to be level with the aft side of the main bulkehead, or els the aft end of the hatch can (will?) drop down on the cabin gusset and on the hatch slides.
Fixing it: molds of foam scraps to extend the coaming with some putty.
Putty out of the mold.
Coaming + putty end shaped and ready for lamination.