I got my son a TruVu set-up off craigslist for christmas and want to use his old 20g as a sump. The tank I got him dosent have an enternal overflow and heard about a DIY overflow idea that sounds nice, but there was little details on how to do it. The way it worked was by notching (they suggested sandblasting?) the top rim of the back side of the tank and cementing an acrylic box to the back to catch the overflow and drain down to the sump. I really like this idea but Im a little lost on how I should notch the top rim. Can I just drill a bunch of small holes or would it be better drill a line of holes and then notch them up a little with a dremel?