Re: Cutting a port hole in bass drum...
Yeah, you want something 4"-6" midway between the center of the head and the hoop. One way people do it is heat up a can (coffee can, soup can, etc.) of appropriate size and just melt a hole into the head. That's quick and easy and leaves a perfect circle every time. I install Kickports in my heads, so I just use the ring included as a guide, and cut it out with a utility knife. With a Kickport, the hole doesn't have to be perfect, either, so it's fast and easy. I've also found that if you stick the ring to the inside of the head, you end up with a much cleaner look on the outside.
Any way you do it, just make sure you're careful