Lowering DT water level question

[Myka]

From your description, you have a glass overflow with acrylic teeth, correct? So if you crack the acrylic, the glass will still hold the water in? Also, you're not attempting to drill the glass part of the overflow at all, correct?

If you answer yes, yes, yes, then it should be just fine for you to drill it. I'd turn the system off while doing it though just for ease of viewing the area. Fwiw, if you lower only a few teeth bottoms, the majority will go through there and will probably make the overflow noisy, so you will probably want to lower all the teeth bottoms evenly.