My spreadsheet predicts somewhere between 7.8 and 8.2 as the absolute max of Universal Clays behind a 125 GDHP. I would start around 7.0 and work up in 0.2 grain increments until my head expansion was where I wanted it...
Universal Clays is a little fast for top performance in bullets heavier than 95 grains. It should prove to be a pretty good plinking powder though...
Are you doing Things Right?
Or doing the Right Things?