Hatch questions

I'm restoring an 1848 sea sprite. I'm decking the front and back. My question is it easier to make the hatch square, or round the edges. I like the way the rounded edges look,might be hard to cut out. I'll be carpeting it after I'm done. When I cut the hatch out of the deck ( using 3/4 plywood) how much space should I leave for marine carpet? I'd like to keep the hatches tight as possible. Is there a rule to leave 1/2 space or so to accommodate the carpet and hatch.

I think either rounded or cornered will work. I did cornered on mine. Carpetng shouldn't be an issue on either. Also I cut the wood about 1/8 inch short for the carpet to fit. If its a little tight it will loosen over time. You can also cut a small piece to try first and get the exact measurement you will need.

I would think square would be easier to carpet as it won't bunch up. As far as tapping I recommend dry fitting and trimming little at a time to get a nice tight fit.