OUCH, Just seeing that hurts!
IF you run the drill in reverse until you are though the gelcoat it makes a really clean hole through the gelcoat, once you get into the fiberglass run it the rest of the way in forward.
Also do the chamfer in reverse.
A Chamfer is a drafting term for a angle as shown above. I had never hear about sanding a radius in but that's a great idea.
Bill
www.MonsterTower.com