Acrylic to Glass with Silicone??

[BCOrchidGuy]

I've built my external overflow but am worried about drilling the glass for the bottom of the overflow. I need a 1 3/4 inch hole but the only glass saw is 1 1/4 inch. I could wait till Monday and see if I could buy the bigger hole saw but for only two holes it seems like an extra expense that I could avoid. I've cut the smaller holes and am going to try grinding them out with the rotary tool. If it doesn't work can I silicone acrylic to glass for the overflow and feel secure in it's ability to hold. The acrylic would be 18 inches long by 3 inches wide, 1/4 inch thick siliconed to 1/4 inch glass.
Suggestions? Ideas? Anything?

Doug