re: Storage out of flat bottom bench seat?

Tinboats.net has a lot of threads with people doing this exact thing.

Things to keep in mind are that the cross benches are structural in smaller jon boats. You're going to want to reinforce it with something if you're cutting into it. You can use aluminum angle and pop rivets, and it will come out nice if you take your time. Cheap(ish) and you can cut it with wood saws. I would frame the hole with angle and then mount hinges to that.

Removing the foam can be messy but again there will be pics showing you what people have encountered and how they dealt with it. Remember that the foam is in there for a reason and removing it will make your boat less buoyant if shite should hit the fan, and technically you could get a ticket from the coast guard but they aren't really in the habit of boarding 14ft flats.