...who's the maker?...i would think that most makers should have their own thoughts on what works best on their own doubles/ribs...

...if you look at the krieghoff/negc websites you should get an idea of the types of mounts typically used on a double rifle...

...there are many variations on the type of claw mounts that you may install on a double (in either ring or rail format, and with or without a base), and it may even be advisable to speak with some noted double gunsmiths for some suggestions...do a search here on double gunsmiths for some leads/names...

...in the dg scope department, i would go with a s+b 1.25-4x20 illuminated flash dot #9 reticle or a swaro 1.25-4x30 ph-series #24 reticle...the cost should be miniscule compared to the cost of a best grade double rifle...