Too weak of a recoil spring won’t necessarily hurt the slide stops function; however, an excessively worn magazine spring will. Try a new and/or different mag and see if that cures your problem. Also, having someone pick out a spring for you would be like having them set the mirrors and seat in your car for you. We are all different and that’s not to mention the different loads we shoot. I would suggest getting one of the spring assortment packs from Brownells and try them all out. Once you know what weight spring likes you, your pistol and your ammunition, you can put together a spring test fixture like the one in the first photo if you like, and accurately measure what its doing over time. If that seems like too much trouble, or your pistol has a recoil master spring system in it, you can just place the hook of the scale in the firing pin hole and measure directly, pull just enough to come off the slide stop, leave an empty mag in so the slide won’t try to come all the way back forward. I prefer a lighter recoil spring used in conjunction with a heavier mainspring. The mainspring along with how the firing pin stop is tuned, slow the slides reward travel, then the lighter recoil spring is just enough to reliably strip the next round off the magazine and feed it into the chamber without the extra inertia of slamming shut that a heavier spring would provide. For me that gives the least amount of sight movement from shot to shot.
