As long as the hammers strike square enough to fire the caps reliably, and the hammers don't shake it's okay. If there is an issue with misfires due to the hammer not striking square this can be corrected by filing the end of the nipple cone to make it square to the hammer face.
Some real fun starts with regulating the barrels to the sights. (1).If both barrels fire to the same plane vertically with the same load, you are way ahead as you may then use only one sight. Some guns will not print to the same vertical plane and then require the use of two separate rear sights.
(2). If you start with PRB this process will be simplified.
(3). This rifle will fire dependably with Bp, Pyrodex, or 777 as the flash path is straight into the powder charge.
(4). Getting the right and left barrel to shoot to the same point horizontally is done by varying the load variables, patch thickness and ball diameter. With any combo of the above there is a powder charge that will cause the rifle to place the right & left POIs to the same area.
I used to have a .54 cal Kodiak and the left and right barrels would not strike within a foot of each other vertically at 100 yards. The .72 cal Kodiak that I have now hits within an inch or so vertically at 100 yards, I'm very happy with it! I have changed the front sight to a much lower height, and use a lower rear fixed sight. This simplifies everything when hunting as there is no problem remembering which rear sight to use with which barrel. These guns are terribly strong and will shoot any reasonable powder charge, the main pressure limit is how much recoil can you stand? With a .715 ball, .010" patch, .030"card wad, and 140 grains of FFg, I measure about 1400fps at 10 feet on my chronograph.
Feel free to contact me if you need more info, misery loves company!!!