Um, well i have set up 2 75g with a 20g sump, 40 gallon sump and currently 29g sump.
So couple of deets needed:
Sump location, if inside the cabinet, prepare for a pain in the butt project.
Basement sumps are so mich easier and better.
Bigger is better, for sumps.
Flow-currently in the 29g sump, i have its pretty much wide open and the hygger 4000 pump, is at ~30%. The overflow is a wierd circular thingamabob that sucks a lot. I hate it but it is what it is.
Hang on back overflows are tricky. Mine would lose prime and the return pump flooded my house 2x. Then I had to get a relay to keep the pump shut off after an outage. Finally I just drilled the tank.