I have been meaning to post these, as I followed the lead of those who went, and cut before. This is how my project turned out. I used a smaller access hatch, but one sized to pass through the crock pot and electric fry pan that we keep out of site, as well as a number of small bins of repair parts.
The steps that I took:
I made a plywood mock up of the outer face of the hatch, and marked center points in that plywood for the hole saw to match the radius of the hatch.
I then moved my "Model" around until I had approval from the boss, and marked the four center holes.
Using the proper hole saw, I cut in the holes as shown.
Using a vibrating saw, and plastic blade - I connected the tangents of the holes that were drilled in.
A little clean up - pop in the hatch, and drill the mounting screws with the hatch as a guide. I used screws and acorn nuts on the back side to avoid a sharp hand hook seeing our reaching in there often.
I then got (no photo sorry) a large bin that would fit, and cut down the one edge so that you can pass items into it via the hatch. Loaded this from the cockpit locker. This way everything is inside that bid for the most part, and it is secure not to move around as we heel.
Anyway, this was the finished project - posted at last.
Russ
s/v Long Story