>>Opening windows solve a lot of problems, but sealing them is not easy, or light.   A trough under them makes this easier. <<

This is the sort of thing where specialist hardware will save a lot of toil. Its not the sort of thing one can manufacture efficiently when the chief concern is building a boat, given the tooling resources at hand.

Builders and yards are using commercially sourced hatches and port lights, even port lights in windows to achieve all important ventilation and security. We are probably wise to do the same