I took the Sharps out today to play with it a bit. The original globe sight was missing the top bar that held the sight insert in place so I ordered a new Pedersoli Tunnel Sight with inserts. Well apparently that sight is higher than the original and it holds the inserts in differently than the original. The rear sight does not have any elevation adjustment but it has a flip up with a sliding sight for different ranges. When its folded down and I use the fixed rear sight I shoot about 6" low at 50 yards. So I tried putting it up and with the sliding sight at its lowest point I shoot about 12" high. I know one solution would be to file down the front post but the that would be the only insert I can use. I'd really like to try the other inserts.
I have an email into Pedersoli to see if they can send me a different rear sight.
I did get a tang sight for it and its nice but not the best for hunting. The aperature is only about .045" so it can only be used in good light.

Last night I was tinkering with the rear sight on the Sharps. The sight consists of a V notch at the bottom of at 2" slide which can flip up and holds another V notch sight that can slide up and down for longer ranges. This is all held onto the barrel via a single screw in the front. The base (rear) of the sight sets in a "cradle" that is dovetailed into the barrel. I loosened the screw and cut a piece of lead shim about 1/16" thick and 3/8" x 1/2" and slid it under the sight and between the ears of the cradle.
Taking it out today I made a really good guess on the shim thickness. At 50 yards the rifle put 3 shots into a clover leaf - all touching and 3" high. That should put me pretty much dead on at 100 yards with the 500 gr bullet I'm using.
I'm still waiting for a response from Pedersoli to see what kind of rear sight options have.