Good morning Kolarshtr,
As you probably know, Promo has the same burn speed as Red Dot, but is more dense. The starting point you're looking for is two sizes smaller than the correct MEC bushing for the same amount of Red Dot.
For example, the MEC bushing chart says a #30 bushing will drop 17.8 grains of Red Dot. If you wanted 17.8 grains of Promo, you'd start with a #28 bushing. Of course, ALWAYS confirm actual drop weights with your scale.
sissy
PS: Reloaders can find bushing charts for MEC, Hornady, and PW loaders in the RESOURCES section of Alliant powder's webpage.