I would use a larger diameter bulkhead. While an unclogged 1 " pipe can handle the flow you want, a 1 " drain is easily clogged with debris, a dead fish, etc, and an overflow is possible, especially if plants are in the mix. You also may want more flow at some point, and you are restricted with 1".
And I would drill the center of the hole lower than 1/2".
The closer you drill to an edge, the easier it is to crack the glass, and you need room for the threaded parts of the bulkheads to turn and tighten. The only time I have cracked a tank while drilling, is when I drilled too close the edge. (it was a small tank, with thin glass though, I have drilled maybe half dozen tanks, from 20 gal to 6ft tanks over 100 gals).
I use 1.5" PVC into bulkheads, and drill the holes about 4" below the edge of the glass, and there is a very small clearance between the threaded nuts and the frame.
I use refugiums on my freshwater tanks, and find them to excellent nitrate users, planting with papyrus, water hyacinth and pothos. (my nitrate levels average 2-5ppm on tanks with refugiums)
I also breed rishi shrimp in the refugiums,which occasionally overflow into tanks, and are great source of extra food. Below is a 20 gal refugium, my sumps are usually 40 breeders, or 50 gal tanks
a different 40 gal refugium
