Much depends on the rifle's and shooter's makeup. Length of neck, bulk of chest and shoulders, length of arm, face structure. Drop at comb and heel + double trigger, single trigger along with weight and balance. It is no mystery why the best rifle makes had "try-stocks".

Sight height and shooting style also come into it, as in a stock climber or do you shoot head high lifting the rifle to your face, rather than lowering your head into the stock. Do you place the stock on the chest, or in the crook between the arm and chest - ie: below the shoulder joint.

Best to try a few if possible before deciding. Pick a trget on the wall, then closing your eyes, snapp the rifle to your shoulder and open your eyes to find the sights aligned on the target you were facing, THAT is a wonderful thing.

Moving and wiggling your head and body around to find the sights and to align them, shows a poorly fitting gun.

I don't have a modern ctg. double, but I've a cheap, stock modified ML double and a couple other guns that fit like above - they are part of me & I shoot them well. Guns that don't align automatically, I don't shoot as well, especially offhand. The double rifle should fit and point like a heavy double shotgun.