Scruffy -
You want to be able to shoot your powerful rifle from all field shooting positions, including prone so that it's full potential can be utilized. If you are unable to use the rifle from field shooting positions, then the rifle is probably too specialized to be very useful as a hunting rifle. My .308 target rifle has the opposite problem, I can shoot it prone, but at 18 pounds it is a bit trying to shoot off hand. Obviously it is too specialized for hunting despite it's accuracy potential to take caribou way out there.
I've shot prone with the .458, 416 Rigby, and the .375 Ultra and H&H. I won't own a rifle I can't shoot prone, but thus far lesser cartridges in very light rifles or with poorly designed stocks have given me more difficulty. Shooting my 590 with 3" Federals prone is much less pleasant than any of the rifles I've owned, as it tends to snap my head back when I have a proper cheek weld.
In the field you don't know what opportunities you will have for a shot. A 300 yard shot is not difficult with a scoped .458, however it takes practice to be able to make such a shot with confidence. Most often prone cannot be used in the field due to intervening terrain or vegetation, although I've used it on occasion. Some supported positions such as leaning across a rock, a large tree trunk, or a mound of dirt or gravel will produce the same stability advantages as prone, with you body absorbing the recoil in the same way. The point I'm trying to make is that not all game shooting is at 25 yards. Even at 100 yards shooting from a rested position will enable you to make a surer shot. Marksmanship is not caliber dependent, so what is true in one case is true in another.
. Get a good solid bag to support the butt stock, not unlike you see F-class shooters use. Take a bit of it to curl around the recoil pad of the rifle,and sink the lower buttstock into the bag. that is, a bag that can be formed. This will take up much of the recoil of the rifle. Let the bag take the shock. 
