Hi omgb. I know this is an old thread, but I stumbled across it in a search for images of sporting sights for my recent purchase of an 1858navy Enfield, armi sport replica. Like most I can only use the std sights if I put the rear sight on the 200yd setting and hold 12" low at 50! If I may, I would like to share my solution to this problem.
I made a front sight ramp and milled a hole in from the bottom, so it fits over the existing sight, then blued and glued it to the barrel with metal filled epoxy.
The rear sight is from an old Winchester Model 70 and is a good height match for the front. I had to raise both sights by about 7/16". Now I can comfortably get onto the sights.
You will also notice the muzzle protector/rod guide. It's machined from a piece of Fallow deer antler.