That muzzle up, muzzle down post may have been one of my posts. In my case it was a warning concerning IMR SR7625, a wonderful powder in semi auto calibers but VERY position sensitive in a revolver case. In my case I was posting about my results loading 38 special with SR7625 and there was a 300 foot per second variation due to the pre-shot muzzle position. BTW, I now load 38 special with Vihtavouri 3N37 and it's proven to be an excellent choice, no position sensitivity problems and it's an excellent shooting powder for 38 special and 147 grain 9mm loads.

Concerning your variation of up to 80 fps, my only concern with that level of variation would be it's effect on accuracy. One suggestion would be to try a heavier charge weight because Pressure can effect the efficiency of the burn with certain powders. Quite simply if the charge is too light you see a larger variation in velocity, something you did not note in your post but you may find this held true in your tests. If so you already have a solution. BTW, I do NOT view a variation of only 25 fps as significant, however I am not capable of what I've seen some really good bullseye shooters do at 50 yards I'm just happy to just hit the target at that distance.