Looks like you're doing everything right, as long as you make sure that shelf is super sturdy, that's a lot of wieght. I see you also drilled the hole up pretty high, presumably so you won't flood your tank in the even of a power outage. Very smart. Be sure to test it a couple of times. I thing the only other thing I'd mention is either make really sure nothing can block off the outflow tube (snail,
macroalgae, whatever) or install a second overflow tube. It'd be a real shame to go to all that work, and then have a major disaster because somthing got stuck in that tube.
Looking good otherwise
