Both Tinker and I have Tolley doubles chambered for the 3 1/2 inch .450 Magnum Express cartridge. Sacrilege I know, but I shoot blown-out 3 1/4 cases in mine, reloads of course. The bullet-jump does not appear to affect accuracy, (with jacketed projectiles, at least). N-for-B ballistics are 350gr RN-JSP at 1950 fps.
At least I have avoided the need for case-trimming!

Most original 3 1/2 inch cases surviving in Australian collections are coiled brass to my knowledge.

The .450 No.2 case is so similar (except for rim thickness) that you would be better off with that cartridge as a preferred chambering IMHO, loaded down to BP ballistics if that is what you require.

Remember that large case capacity was an advantage only if you were looking for increased velocity with black powder, or had to cope with the pressure increases of cordite in the tropical heat. With modern powders, extra case capacity is a pain in the proverbial, as it has to be filled with wads or filler. Modern nitro powders allow fully 2 tons less pressure for the same ballistics in most N-for-B loadings, and the Hodgdon 'Extreme' powders are temperature-insensitive, so the big cases are useful today only if you're shooting charcoal.

If I were custom-chambering a modern double for a .500 with N-for-B ballistics, I would probably consider cutting it down to 2 3/4 ! ....and it would still need a filler wad!