Yep-he's got 'em-the best thing that I'd suggest would be to bench-fire your P5 at the distance that you expect to be using it at on a gridded paper target, and then do the same shooting offhand. Then call Earl's with targets in hand so you can have a good discussion on which replacement rear sight would work best for you. They're fairly easy to install, but at times i felt like I needed 3 hands. I'm sure that Earl would install it for you for a very nominal fee if you sent him the slide.
Best, Jon