The barrel is the same size from their .54(28)bore up to their .62(20bore) this adds a bit of weight. That said the gun should still be in the 7-8 pound range, a might heavier then the originals.
Still you have a thick breech and can handle any charge your shoulder can take.
This will be a fantasy gun, so if it was just a tad heavy for you you could cut it back to forty inches in be in the ball park of its .62 smooth weight.