If you drillout the nipple, be careful not to drill all the way through. I've found that just giving the bottom opening a bit of a flare helps more than enlarging the entire hole. Think "countersink." Something about nozzeling effect I learned from designing rockets over 50 years ago.
Armed and Safe: Not just a theory
If it time to bury them, it is time to dig them up.
Remember, "Behind every blade of grass."