I also noticed that the mainspring and rebound spring must "balance".........I dropped in a light rebound spring with a stock mainspring and it did not reset the trigger. With a lighter mainspring it worked just fine.
The Miculek rebound and mainspring set is supposed to be perfectly balanced for fast DA shooting, but I haven't tried it. I have Wilson Combat springs in a 10-14 that work well.
Ironically, one of my best shooting revolvers is one that I added a heavier rebound spring to. It's a Ruger GP100 DAO that had a sluggish trigger return and a very stagy DA pull, so I clipped two coils off a S&W rebound spring and installed it. The DA pull is heavy but now VERY even, and I shoot extremely well with this gun. Lighter is not always better, heavier springs can actually even out the DA pull.
I actually don't like too light of a DA pull, it makes the trigger feel like a cap gun. A consistent, even pull all the way through without any "flat spots" in the trigger stroke is more important than the pure weight of the pull.