It might be easier, and cheaper, to build a Double Flinter in an Over/Under configuration, but it would not appeal to those who want the classic lines of a Side by Side. I have read claims that regulating O/U doubles is easier than regulating the barrels on a S/S, but have no personal experience with this. I have seen one " Turn-Barrel " Shotgun built on a Leonard Day action, But I didn't see what gauge it was. It would be a faster second shot than reloading the first barrel, but not as fast as having two actions cocked and ready to fire.
Personally, I don't mind a bit of " chunkiness" in a SxS double if the gun is balanced. I saw and handled an original Tower flintlock DB shotgun that had 36 inch barrels, and balanced on the forehand where you naturally placed you hand. I still don't remember how much the gun weighed, but it had to weigh 8 lbs. or more, and it swung like a dream. So, I know these guns can be made right, and that they can be fine shooters. I suspect that there are alot of shooters who just never learned how to shoot flintlocks, and don't want to be bothered learning how now.
The average Modern breechloading SxS is going to cost you $2,000 an on up, so people wanting a DB Flintlock SxS shotgun should be expecting to pay much more than that at lest double that amount. I don't know many shooters who can afford a gun at that price.
