Optimum water level for a stock Orca 250?

[H20ENG]

I'll be using one on a clients system. It'll be draining back to a 24"H sump. I was wondering how high it should be off the floor to maintain optimum water level inside the skimmer.

I hope to run the outlet wide open, so there are no floods on startup before it begins sucking air. So, the standpipe height needs to be pretty close.

Thanks all,
Chris