That'll work!
Which is kinda what major powder companies do after producing a new lot. They save some of the previous lots that were faster or slower-burning than the ideal they were, uh, "aiming" for. They test the new batch, then if it's not within 2-3% of the burn-rate desired, they mix in some of the older batches to adjust the burn-rate.
This obviously is easier to do when the powder's been in production for a while, so there are more previous batches. When Hodgdon started offering the IMR Endurons a while ago (primarily due to a shortage in the supply of the Australian-made Extremes), they sent me some 1-2 pound samples of various powders to try. One of them was IMR4451, which was designed to approximate H4350. I was impressed enough to order an 8-pounder from a website, but it resulted in around an 80 fps difference in the same loads. So I mixed the first batch into the 8-pounder, and it resulted in velocities closer to their published data.
