I had to put a drain hole in my infusion mast. I did something like what Jake said. Problem is the mast is open (for the diamonds) at the bottom and I couldn't see how the foam plug to determine where to drill a hole in the bottom.
The infusion also has a plug at the top, I learned this after drilling off the mast cap. I put the drain hole below the foam plug.

I put some marine sealant on the rivets but it came right off... what will stick better? 4200?