Originally Posted by chef2sail
All great points. Especially the insurance and surveyor one.
I think the holes the OP is referring to are the limber holes in the cross pieces of the frame in the bilge. I have the exact same boat as he does (C&C35 MKIII). Whether these are actually called structural stringers, I am not sure ( I think they are). This frame is what the floor is screwed into. The limber holes allow the water in the boat to drain into the bilge.
Dave is correct I'm referring to the limber holes. Our bilges look very different as chef has the c/b model.