Right, thanks therother and Dorkus - the equations worked great. Therother, I plugged it into a spreadsheet and checked a good dozen points, everything was good to within what one can tell with the 5% rounding, including with an adjustment for Normal unit size. I even made a table - 10% to 80% X 1k to 32k population - and right down the 80% column is what you said, Oaty.