Hello Westley375
I was the CEO for Cast Performance Bullet Company a few years ago. I have no experience with the 470 Nitro, so I can’t recommend a powder charge, but I can make an educated guess that you would be very well served with a good bullet mold and cast bullets. The pressure and velocity of the 470 is about perfect for cast bullets. You can use gas checks for the 475 Linebaugh and 480 Ruger and LBT Blue lube.
Cast bullets at the same pressure will usually give about 100 fps more velocity than jacketed, so that will probably effect the regulation of a double. If I were doing the work for myself, I would opt for a mold to throw a bullet about 50 grains heavier than your jacketed bullet, so as to keep the velocity about the same.

50 grains will not produce much more recoil because the pressure is reduced over jacketed bullets, and they by working with your powder charge, you can probably get very good point of impact at point of aim.
Amway, if I were you, I would absolutely go with a mold and have some fun.
Steve