It's not the right application for that powder. Universal (and Unique) are for subgauge (16, 20, and 28 gauge) and 1 1/8 oz 12 gauge loads. You need a different powder for 12 gauge 1 oz. There are many that work well. Titewad, Clays, ClayDot, RedDot, Promo, and others. Check the website loading recipes for Hodgdon and Alliant.
In 12 ga., Universal is indicated for heavier field loads. That's probably why you're not seeing any 1 oz. recipes for it. Universal's sweet spot is in 20 and 28 ga. target loads. In 12 ga. 9/8 oz. target loads it requires a significantly heavier powder charge making it much less economical than the faster powders such as Clays and International.