how about this sump design for a 75gal

[captainken]

30 x19hx 15w. sump

using a external iwaki pump
and a extrernal protein skimmer lifereef.

[captainken]

arrow to left is the skimmer return tube.
arrow to right is the return to pump
tube at top left is the overflow return tube,
flows left to right.

[blueface]

Looks great but I would personally eliminate the last 2 baffles from the middle - too many baffles will slow the flow of water. It will also give you more space in the middle for live rock or refugium and internal skimmer if you ever need to run one.