Shooting from your "hind legs like a man", is a Harry Pope quote. In addition to being possibly the best and most famous American riflesmith of his day, Pope was one of the best standing offhand shots who ever lived. But he wasn't shooting elephant guns. Just
Schuetzen type matches during their first era of popularity, using relatively (by modern standards) mild cartridges. I have no idea whether Pope ever fired any of the 4-bores or bigger Nitro Express cartridges but assume he would have been standing if he had. The recoil pad hasn't been made that would get me to shoot one of those off the bench.
I once read a piece by (or about; I've forgotten) an African PH who got tired of newly minted safari hunters with more money than sense showing up with a new 460 Weatherby and asking him to sight the rifle in for them. He took the attitude that if they hadn't even done that, he wasn't going to take them out to unsuccessfully flinch their way through the hunt, but would loan them a .375 H&H or something a little more manageable to start out with.