What's stout?
There's really no reason to shoot anything hotter than a 520 grain lead bullet over 68 grains of black powder, or the smokeless equivalent.
Personally, I think the .45-70 is brutal off the bench, especially if it has a steel buttplate. I've taped an old Pachmayr onto a Sharps to sight it in, because my shoulder was getting really tender from being slammed.
However, I also think it's no sweat to shoot offhand, from sticks, seated, or any other position that allows your shoulder to roll with the gun. The recoil is a long, hard push, so your body can roll with it, as long as your body is in a position that allows it to move. It's a fun gun to shoot from those positions, and my shoulder has never complained at all, even with a steel buttplate.
Those old crescent buttplates work well, because they enforce proper hold. If you don't hold a rifle right, a .45-70 will let you know! However, if you use proper technique, it's fun to shoot.