I'm running the 18lb spring on mine. Although Wolff recommends the strongest spring that functions reliably, that 20 made the slide just too tight for my liking.
I don't know if would help you or not, but when I was shooting low/left, I came across an article that recommended paying careful attention to your pinky since you may squeeze with it a little as you pull the trigger. What I do now is put my right (trigger hand) pinky over my left, and it helps!