I have a old 100 gallon(6 ft) tank with a slate bottom. I'm thinking of drilling a 2 1/4 in hole in the slate bottom, then siliconing in a 2 in PVC pipe for the overflow. Then I plan to put a 4 in ABS pipe with a cap over the PVC. I'm thinking of drilling a bunch of 3/8 in holes in the bottom of the ABS pipe. Anyone tried something like this? Thoughts?