I'm a norwegian and new to the forum, but had to make a reply here. I hope it could be of some help!

1. Scope on a heavy hitter..? I'm thinking of putting a scope on a .416 Rigby, but would leave a heavy double whitout.. However, I suppose you've made up your mind, so the ONLY right mount on such a weapon woud be a german claw-mount! I have one on my drilling, and it's a joy to use. The best there is, and well worth the cost! It also won't ruin the looks and value of your gun.

2. Type of scope: I'm used to european optics, Zeiss on rifles and binos, but on such a rifle you would v be better off to use the small 1,5-5x20 from Leupold. Here you get adequate eye relief to shoot the gun well.. I suppose you want a comb that accomodate open sigts aswell, and to put a Swarovski with a mere 7-8cm eye relief would most certainly give you a blue eye... A Leupold is also small enough to be carried along in a pocket when not in use. And add little weight to the gun: i e won't mess up the point of impact.. I've heard this is more of a problem with lighter calibers? "Highend" scope: A Leupold matte, german no.4 would be considered highend in Europe, the optics are bright enough for whatever you want to hunt with a .470! Shooting cape buff in the dark is a bit risky

Good luck with your double! I look forward to get a DR myself in not to long

Great forum by the way!