Plumbing--need your help

[Slick Fork]

I would avoid ball valves on the return lines, you don't want to be restricting that flow at all.

I would also recommend some sort of glass overflow, do you remember how mine was set-up? You could do something like that and not lose a whole lot of real estate using the lower hole as the primary drain and the upper hole as a safety. It will look better and be a little more functional.