Hm, fair enough.
Just ordered the drill bits, bulkheads, and gravel, as well as some loc-line for my returns. Point of no return is back that way...somewhere.
The budget I'm tallying up is a little more than we'd anticipated (no local source for Black Diamond grit), but still on track.
What I'm thinking for the returns is they come out inside the overflow box, but the loc-line carrys them over and into the tank. If that doesn't work out (physically doesn't fit or whatnot), I'll go back to the original plan of boring through the overflow box, but still use loc-line to adjust the flow. Gives me more options, anyway.
Thanks for all the input, everyone - I will post updates in my tank thread (will link to it once created). This is starting to get a little off-topic.