Barry - I have peeps on all my sidelocks both flinters and cap locks. I have 3 styles. The T/C 7194, Lyman 57 and williams (model ??). I find I can shoot much more accurately with them. And a plus with me being a lefty is that the peep blocks a lot of the flash from my flinter and I can shoot those better than without one.
I'm sending you a PM.