I bought a $10 port adhesive template at my drum shop where I take lessons, along with a drum specific pillow. It was effortless, and it came out perfect. I would definetely use a template if I were you. When you are cutting, the knife tends to want to follow its own path on a straight line, but the template is thick and it forces the knife to go along the round path, which makes the cut nice and smooth. I feel like it would be very difficult to achieve the same result hands free following a drawn circly only.
With this template adhesive thing, it also prevents further tear of the cut area because it stays in place after you are done cutting (you're supposed to do it on the inside of the head, but I figured that out too late, so the template is showing on the outside. I will take a pic and post shortly when I go home for lunch)
Try to look at youtube, there's a guy making a porthole with a tin can or so. Looks really fine. The one time i did it, it went pretty wrong.... i cut wrong, so had to make it another place. And the hole was pretty... what can i say... the edges were uneven atleast... that pretty much covers it. I did follow a small bucket...
if you can't spend the 10 or 12 bucks on a holz unit, the can method is best, But they can rip easily, what i learned 20 some odd years ago, grab some old heads, with a can about 2 inches bigger than your intended hole, heat the can on the stove, pick it up with an oven mitt, and burn it thru the old heads twice to make two big circles of head material. Use some spray or brush on contact cement and glue one patch on each side of the head. Then take a smaller can and burn a hole through all three layers. This will give you a very strong re-inforced hole.
To add evn better looks, get some black material and cover the hole from the inside. Here is an old pic of a young me with double holes done this way.
Trace a small circle in place. Cut out most of the hole not near the line with scissors and then with room to work, cut the rest with small fingernail scissors. Cover or it with a Holz or like device to protect the hole. The can works but if you drop it or tilt it while using it. Damage.
this thing is super cheap (like $4 US) and makes hole cutting easy. it's a flat ring you just stick on and cut the hole out using the inside edge of the ring as a guide. the ring stays on the head as a reinforcement. it's similar in concept to holz, but even cheaper.
She's an arts & crafts whiz. She's never let me down when it comes to cutting a nice clean port hole. She then traces the port hole and melts the edges down slightly so it isn't so rough and doesn't tear so easy.
There's a trick to cutting port holes, but I dunno about "6 holes. Heat up a can to the point its hot enough to melt plastic, and just press the mouth of the can where you want your port hole. This will make a PERFECT port hole very easily.
So if you could find a 6" can, you could get a 6" port hole. A lot of people use torches to heat up the can, but a stove eye works just as well. It just needs more time to heat up, and cools off quickly.
If you decide to try this, use gloves, and something sturdy to hold the can, or you will probably burn your hand pretty badly... I will shamefully admit I found this out the hard way...