May I ask what the driver is for the tang sight? I ask because, a tang sight is generally adopted when considerable elevation may be involved. With a pistol caliber lever gun, do you intend shooting beyond 150 yards ?
I'm no fan of buckhorn sights, so perfectly understand if an aperture rear sight is an objective. Cosmetically, a well made tang sight can be quite pleasing, so that's also a consideration.
But for a pistol caliber lever gun, a vintage Lyman aperture sight mounted on the receiver, a Williams FP sight, or the Marbles Bullseye rear sight (mounts in place of the Buckhorn sight) might all be functionally and economically more suitable.