You do want to make sure the holes are true and round with no imperfections. Any little chip or out of round adds lots of stress. When water is added the pressure is pulling the hole apart as the glass flexes out and round is better to distribute. Otherwise you might end up with your tank on the living room floor one morning. And of course the least number of holes per side is better. There seemed to be a few threads on tanks cracking over time and speading from the drilled holes. Just my thoughts.
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