As has been noted previously, I have a Kreighoff "Teck" boxlock ejector O/U double rifle in .458 Winchester Magnum which I acquired in 1971. It has interchangeable barrel sets in .375 H&H and 20 gauge 3" magnum. I have used it to take four of the Big Five (my rhino was taken with a bolt gun) with totally satisfactory results. (See: http://www.frappr.com/?a=mygroups&id=3823381)

Both sets of rifle barrels are scoped in claw mounts and I have never had the need to resort to the open sights. My longest shot was on an eland, at some 240 yards, and I have also used it to take greater and lesser kudu at relatively long range and under demanding light conditions.

Having used O/U shotguns for over 40 years, I find the O/U configuration completely normal and have never experienced any difficulty with it. I am presently having two more "Teck" rifles and an "Ulm" sidelock rifle built in calibers .500 NE, .450 C&W (a wildcat cartridge of my own devising) and 9.3X74R.