Joel,
yes I tried lowering the boxes so that water could get in there faster (more tooth area but they still filled quickly.
I'm back to using the Rio as the return pump with actually only one return box (more space in the tank for even more corals now! lol)
I also figured out what my air problem was - lid not cranked down enough so everything is under control. The sea swirls are swirling on a closed loop and the little rio provides a gentle flow through the sump