Rather than drilling 2 1/2" holes why not just drill one hole for 1" or 1-1/2" for the overflow? Then for return line drill a hole for a 3/4" bulkhead fitting?
Ok, this may be a stupid question but I'm going to ask anyways... Are you sure the glass is not tempered?
Its an acrylic tank....
got it completely drilled and plumbed last night BTW-- just need to do my sump dividers and give it a wet test and im Good to go
Very nice! Just didn't want to be quiet if it could cause a fail. I look forward to pics and details. Looks very interesting.