No Don't cut!
I too have an O'Day 22. Yes, I have noticed the 2" hole in the deck of the cabin and yes it is the only access you have to the bilge. I have had mine in the water at a marina for two years now and only pull her when a hurricane blows in. And yes, I have found it to be a pain in the butt to pump her out once she fills. However, I have found that using either a hand pump of a electric bilge pump works just fine. If your boat begin to take on that much water the bilge is filling quickly; One of several things are happening.1. You have a bigger problem than you want to have. Pull the boat, put her back on the trailer and use only on the weekends or sell her quick.2. You are not paying attention to her and allowing her to fill. The O'Day 22 was meant to be a trailerable day sail boat, cutting something in the hull is not a good idea. A fellow owner of an O'Day tried putting in a bilge and had to cut far to much out to get to it for my or his liking. I suggest you leave well enough alone.Best of luckKevin Meadows "Alcyone"