Nevin's 14G + 5.5G sump

[Nevin]

Any opinions on the plumbing layout and Mag 2 vs. 3 before I start putting it together?

I'm not sure if I should be worried about syphon from the return. Is the check valve enough? Would an airline inserted down the return work to bring in air and break syphon if the pump shut down and check valve failed?

By the way, comments about biocubes in a previous post here weren't intended to disparage those who use them. I know some people do amazing things with them, it's just not the way I want to go.

Regards,
Nevin