Patched RB in a double works just fine, as long as it loads OK, choked or not. If it goes in, it comes out.
; I turned an old damascus double into a side by side double smooth rifle for hunting deer and bear. Although it was a 2 1/2" ctg. gun, the loads (Black Powder)and wad column are identical to if it was a ML. IT-too, like Rebels ML, shot very well indeed. I'd shortened the barrels to 24". just like the many of the African 12 bore BP doubles. The standard loads for the early, 1880 to 1900 BP loads for RB were 150gr. for the light load and 7 drams for the heavy load. In a BP shotgun, I'd suggest only up to 120gr. with a single patched RB. Buckshot works pooerly on bears, so I don't consider it for anything other than home defense.
; A .715 ball(only if it passes the choke) with overshot card and fiber underneath might shoot well, but a .690 with patch will generallygive a tighter shooting load, generally. You can adjust the powder charge & wads to get the barrels to shoot together, or well enough for hunting, normally.
; As well, Lee makes a .690RB mould, and their cheap to buy.
: The guys I hunt with, use my WW.684RB's with modern-type loads in their pump duck guns for moose if one shows up while duck hunting. They clocth patch them inside ordinary shotshells and claim 4" groups at 50yds. Message me for the load if interested.