Stick with the specific bullet maker recommendations. I'm inclined to mix 'n' match with other calibers, not with .454. With the .454 it is sometimes not so much about absolute pressure and the gun as it is about the specific bullet's ability to handle that pressure when it is passing through the forcing cone. That even varies within maker. You can't run both Speer 300 grain bullets to the same pressure. You can't run both Hornady 300 grain bullets to the same pressure.
Tom
