Wasn't there a thread on Speed Talk (may have been yellow bullet) where they took one head, flowed it and then it was shipped around the country and flowed by anyone who was willing to pay the shipping to the next guy. Or something like that.
Anyway, when all was said and done, I think there was said and done, I think there was a 2% difference across all the benches from all over the country.
I point this out because if the guy operating the bench isn't an outright liar, or his bench isn't junk and he is using Audie or Performance Trends you can use flow numbers to look at general tendencies among several heads and across several benches.
Still not the only numbers I'd like to see, but it at least gives you a starting point.