Thanks for the help. ultraman, by eyeballing it 3mm on each side seems like enough. They almost clear, they don't need much.

Now I have another question! How do I remove the old BB? I tried unscrewing the plastic side but it crumbled almost instantly. Then I tried unscrewing the metal side but it's as if the tool isn't fitting correctly. The tool falls out of the splines anytime I try to apply pressure. I'm using a Park BB-22 tool and I'm fairly certain it's a Shimano cartridge (square taper) BB. What am I missing here?