Agreed - there's no reason to risk it, and really nothing to be gained. I was only curious because I just started reloading .380 and I noticed that so many of the recipes were only a single value, rather than a range of charge weights.
If for whatever reason I wanted more speed than W231 can give me, I'll just use Power Pistol. But this is just going to be range ammo, so I'm not that concerned. I just made up 10 rounds with 3.2 gr of W231, 10 rounds with 4.2 gr of Unique, and then ten each of Power Pistol at 4.2, 4.5 and 4.7 gr. I'll see which one is the most accurate and stick with that.