I built a .54 caliber plains model as a kit about 15 years ago and used to shoot it extensively. There are only two issues with gun.
First, the gun is a little large if you have short fingers. The shape of the stock is such that the trigger is a good distance from the back of the stock.
Second, the grooves are shallow. This makes the gun more sensitive to the texture of the cleaning rags. Normally, the gun would shoot into 4 inch groups at 50 yards. However, one day I couldn't keep all the shots on the 30 inch square backer.
That morning, I was using some left over scraps from my newly-sewn shirt as cleaning rags. Evidently it didn't have enough nap to clean the grooves, because as soon as I switched back to my usual cleaning rags, the groups tightened right back up.