See a lot of 3/8" holes for the ports used in pots. Equally spaced around the perimeter, with one in the center. I use several port designs, I prefer four 3/8" and four 1/2" drilled equally spaced opposite each other. Of course this is for the dual purpose pots I make, as there is also a 1-1/2" hole in the center which acts as an access hole for the secondary striking surface.