Cutting toothless weirs in back of tanks with a Dremel for external overflows

[Megalodon]

I have a 90 gallon tank I'm putting two external Herbie overflows on. They will be 25cmX20cmX11cm. The tank glass is about 1cm thick but the overflow glass will be 6mm.

I was going to drill the tank and have 90-degree upturned PVC elbows to bring out the water to the overflow boxes, but they will not have as much surface skimming area as the weirs would, almost 2.5-times less, in fact. Not to mention, others have told me this could be noisy.

Then again, others have mentioned that cutting weirs in the back of tanks can weaken it and possibly cause cracks.

In any case, which is the better way to go? And if it's weirs, then how do I do it? I have a diamond bit to drill small glass holes, and I also have a tungsten carbide bit. Will these work or will I need a glass cutter? I'll also need to cut out chunks of the upper plastic rim, which I'm not crazy about.

Please help. Thanks.