ok then not you but an experienced driller from a lfs..for like 30 bucks they come, drill it even if there's water in it and they have the $$$ tools.
An overflow isn't appealing and isn't safe...sure it can go well for years but the risks are just too high.
I can't drill mine since it's an old school braceless all tempered glass tank..all sides ! It would explode.
Still, i don't use an overflow..(even tough i built some and tried at first ) ..i prefer my only other option : a drilled sump placed higher than the tank..at least i sleep better