Thanks once again for the suggestions and helpful photos. I have a copy of the Nicro catalog, and your suggestion of the screw-in type offering the alternative if a passive or solar vent sounds like the way to go. My boat stayed dry and mildew free this winter with only one beat up but functional jury-rigged Nicro passive solar vent in the bow. That vent was adapted to fit the original stock deck ring with a lot of silicon goop added. To do it right, I will have to cut the opening to 4 and 3/8 inches it appears, but once I do thatm I will have a lot of flexibility. Still it would be nice to find a cowl vent to fit the stock deck ring that I already own.