I don't like to cut on springs.
Order a reduced power spring form Brownells.
That way if it doesn't work out you still have your original to fall back on.
I think it's better to spend a few bucks on a Wolff. I bought the Calibration Pak, put in the 17 lb spring first, found that it gave a lighter DA with reliable ignition and have not tried any of the others, running from 16 to 19 (20 is stock.) www.gunsprings.com
Or order a Wolf Spring kit and install it, don't go whacking on springs, its a good way to compromise the relability of your weapon. It's kind of like backing off on the main spring strain screw, on Smith & Wesson revolvers, don't do it.