Most folks have their own pet theories about what constitutes optimal flow through the sump, the vast majority of which are neither based on any credible science nor reproducible from tank tank. That's all to say that it really doesn't matter. As long as you have enough flow to ensure even heating and adequate display surface skimming you're good. As soon an competent intank circulators made their appearance in the hobby, I went to much lower turnover numbers. My current tank holds 400 gallons nominally in the display and my main return pump nets 1,400 - so 3 1/2 times. I've yet to hear a cogent argument for higher flow; just seems like a waste of electricity.
Oh and for folks that still think it's important to match sump and skimmer flow - never heard a cogent argument for that either.
Oh and for folks that still think it's important to match sump and skimmer flow - never heard a cogent argument for that either.