The bilge drain is located no more than a half inch from the bottom center. The hull itself is about a 3/8" thick there, and the lower lip sits about 1/4" higher. When I feel inside the hole, the hull is just slight lower. The following picture shows the location, lower hole. The higher hole is the mooring drain from the cockpit.
When you drill the hole, you will go through wood, so take out a bit of wood, not the fg skin, then refill with fg goop, then re-drill to make a smooth fg lined hole when the fg has cured. BTW the wood is sealed between the inner and outer skin of fg so if you remove wood using a Dremel tool, then re-coat it, it will remained sealed against water intrusion.
