Cool, I like your idea with 4lb
Torch has a point. Dang engineers. You could brace it out somehow but at that point you may as well ply and glass then foam.
So to be clear are you foaming all compartments.
Why 6lb foam vs. 4 lb foam
Yes you should take the time to seal with poly once tops are cut down to height.
Never used a router to edge off the square edge but wished I had. I ended up using a sander to round off the edges. Takes awhile like that and inconsistent edging. Go for it.
With epoxy I started with the heat lamp to cure and follow up the next day as I was doing something else. Epoxy eventually cures I'm not so sure about poly?
Revisiting pic you sent. What about a pc. of quarter round with the curve on the hull of the boat, then glassed.
Looks like it would fit right in there.
