I cut the holes in the glass to start with, they weren't *technically* already existing. LolI would much rather use a table saw to cut ~1/8 off the top of the inside weir box then dork around with the existing holes in the glass.
However, I was able to grind the holes a little larger at the bottom, so that now the weir fits (snugly, mind you). I had bought thicker/ larger gaskets from BRS already, and used those against the glass on the outside, and I'm not seeing any leaks yet. Btw, the water level in the tank to get over the slots in the weir almost completely fills up the overflow, is that normal?