I had a Ruger #1 in .416 Rigby. I was unhappy with the factory sights, and the factory quarter rib positioned the scope too far back for me. My solution was to send the rifle to a gunsmith who made up a custom quarter rib inletted for Talley QD rings, and positioned so the ocular lens of the Leupold 1.5-5X was in line with the forward edge of the falling block. Thus positioned, I could use the scope up to 3X, there was no chance of getting hit, and there was nothing in the way of the loading port.

I think your idea of the medium eye relief scope is a good one. My .375 wears a Burris Scout Scope, and I am very happy with the arrangement. I would use a steel mount screwed to the barrel - most big bore Ruger barrels have lots of meat, and this could be augmented with some bedding compound or silver solder.