First off, 3/32" is much bigger than necessary and 1/32" will suffice. If you don't have small bits, 1/16" will work fine. I position the vent hole ~1" above center on the bulkhead, the theory being that it's unlikely that I'll ever have more water than that in the cockpit and when the boat is inverted (such as in a rescue situation), the water will never reach the hole, since the cockpit will empty.