Here are some thoughts from someone who is currently refurbishing my Phantom kit. I think I'll take his advice and see how things turn out.Of course, my preference is to not cut any holes ... I love the sound of a booming bass drum when I'm not mic'ed—most of the overtones dissipate and all that's left is pure tone and thwack. It's a bit louder on stage, but recordings reveal that it's just right out in the audience.But the sound men I've dealt with prefer having a hole, and I'll admit that it's just easier when there are only five or ten minutes for a changeover.Anyway:"For a 22" head I wouldn't cut (the hole) larger than 7 or 8 inches. Also I'd offset it to one side. The offset will maintain the "punch." The air column created inside the drum by the pedal beater strike will reflect off the resonant head rather than exiting straight out. The smaller diameter will help retain some of the low end."
Update:
I've taken this advice on the three Slingerland kits that Steve Schmitt has detailed for me. It works great.
Each front head has a 6" hole in the lower left quadrant (from the player's perspective). I'm rarely mic'ed and there's still quite a bit of resonance. On the few occasions when I've had an engineer, he was able to place a mic easily and I could accommodate his request for a small towel with no hassle.
The head setup for each of these is a clear Powerstroke 4 batter with a clear Ambassador front. When I'm running without a mic, I don't use a towel, and I get a rich, round thump. Your results may vary.
In a perfect world, I wouldn't have a hole. A good sound engineer shouldn't need that crutch to get a good result. But when I need a mic, my band is usually in a support role, and I don't want to be the cause of any delays. Anything I can do to make a sound guy's life easier will probably pay off during the performance.