Drilling, should I be concerned about strength.

[Sasq40]

So I've done all the test and the bottom of my tank doesn't appear to be tempered so I'm going to attempt drill it. Now I'm kind of wondering if I should be concerned about these holes weakening the glass and causing a issue down the road. I plan to have a centre over flow with a 1.5 drain and two 3/4 returns. Will these holes cause any issues of concern related to strength and possibility of something happening down the road.?