I'm with the buy Wolff springs camp if you want to tinker with springs, but there are many ways up the mountain to also include bending and grinding them, and shaving down the strain screw.

One note of caution in doing anything to the older S&W mainsprings, say, prior to 2000 or so; I've found that current factory mainsprings are thicker compared to the old days, and the result is a heavier and sometimes hitchier action. They're not making the old mainsprings anymore and I'd leave them be.