I don't load for .454 Casull, but I've been playing with the data in QuickLoad. I don't think you can double-charge a case with Bullseye unless you are doing light loads to begin with. You can stuff enough BE powder in there to get yourself in trouble, but a compressed charge is not as high pressure as one would expect.
Bullseye has always been stable and predictable for me in high-pressure cartridges. I wouldn't have any trouble with using it in the .454, but I don't think I'd max it all the way out. There are too many other good powders out there.
"The only way to stop a bad guy with a gun is with a good guy with a gun"