I cut a rectangular opening in the locker floor, sized so a hinged hatch would fold against the cockpit wall. It has made working in the locker (access to fuel hoses, vents, ventilation, wiring) easy and also allows me to store a portable SCUBA compressor in that space. It would be more useful for ER access on other boats than ours because weI added a 55 gallon flat tank on top of the original fuel tank, raising the floor about 11". I have a lot of machinery crammed into that space under the locker (ventilation fan, refrigerator compressor, hot water heater, steering cable run, and compressor storage) and the floor hatch is a great idea for easing access to all this. I had to fabricate an aluminum support stringer to take up some of the load from the locker floor.  This is made from angle stock and runs under the floor just outboard of the opening.