Here is the amount of powder that I'm using:
Talked to Tommy at Leadheads. He claims there is no need to do anything but the following.
300gr bullet use 51gr of IMR 3031
425gr bullet use 40gr of IMR 3031
I've jumped the 300gr bullets to 53gr. It hits in the same place but I get the occaisional flyer. Though I will say that there is less unburned powder with this charge. I'm thinking somwhere between 51 and 53 is the sweet spot. I have too many guns that need shooting, is my problem.
Good Luck
Tom