My New 72"x20"x20" Tank Build

[mark]

Can't say nothing about the Herbie as but to listen to Untamed as he's experienced with running one.

For the return you should be able to reduce pipe diameter one size to make a little more manageable after the top Tee, build a manifold (such as like here) to even out flow and with multiple outlet not have a great loss.
RC calculator might be a guide.