hanshi,
I have an original rifle similar to what you're considering, so I'll give you some dimensions, and that might help you with some idea of weight and balance. The rifle is made with a single bolt percussion lock now, but the barrel is on it's second use (at least) because it has a notch filed in the bottom flat for the forward bolt on a flintlock.
The barrel is a hand made one and is 44 1/2" long. About .40 caliber. The breech end measures .952", the muzzle about .895" and the waist of the swamp is .812", and that measurement is 7" back from the muzzle.
The overall length of the rifle is 60 1/2" long. The LOP is 13 1/2" to the front trigger. The rifle weighs about 8 1/2 pounds, and the balance point is 30 1/4" back from the muzzle, right about where you'd expect at the area of the rear sight and RR entry pipe.
This gun points and balances pretty nice, not overly muzzle heavy, but if you're concerned about weight and muzzle heaviness, I'd certainly consider a lighter weight barrel than this one.
John