I have the springfield longlide v16 in .45 super, and I still wouldn't try it. Not to say it wouldn't be ethical if done properly. But I'd much rather haul my 6" .357 mag, or 4" .45 colt revolver for the task of "deer under the tree stand" hunting. It is a definite concern, if the big buck is directly under you and you cannot position your rifle in such a way as to take a shot. I'd go for the spine in the neck area with my handgun if that ever happens. Plus, with the revolver, I can put a cylinder or two of shotshell rounds for the opportunistic squirrel shot.
Still, if I was gonna do it, like the man said, I'd get some 255 LSWCs made for .45 colt and press them into service in a .45 super load, pushing them out at 900 give or take.