I think the caliber is ideal for a scope.

Question: does your Merkel have precut (what do you call these) "gaps" "holes" for scope mounts? Most continental model SxS double rifles have little removable areas on the quarter rib where a scope can be mounted (this makes it much easier and cheaper than having gunsmith cut into the rib). Your choices are for claw and rail mount, or a EAW style pivot mount. I prefer pivot mounts (I have one on my 9.3 SxS by Chapuis), there are much cheaper and you can use different ring sizes and use whatever type of scope you want. You can have it done by JJ at Champlin, or New England Custom Gun (they import them from EAW, so you can buy them and have someone else do it), runs arround 300-400. Claw mounts are about $600 or so. Rail scopes by Zeiss or Kahles are also more expensive, so they also add to the cost.

Now for the eternal question: do scope effect regulation?

In my limited experience (one rifle) mine was not regulated for a scope. But I've found with a light scope regulation is not really affected (some "stacking" of barrel groups, ie one over the other rather than side by side) the groups remain the same, as far as I have tested to 100 yards. I have a 1.5-5 Leupold Var-III and a Burris 4X compact and they both work well with the pivot, totally detachable, keeping their zero.

Hope this helps!