This is a very interesting thread.

I'm assuming the Merkel Double Rifles have over hanging sears like the shotguns.
It has always been my belief that the over hanging sears prevented doubling. Is doubling common with most doubles, or just Merkels?

I've never worked on the rifle but I had the stock off a shotgun yesterday and it looks to me like the sears would be forced deeper into engagement under recoil rather that out.