Cutting the hammer should actually prevent light primer strikes.
Since the JP springs are made to have less tension than stock springs, the hammer accelerates slower than it normally would, sometimes resulting in light primer strikes. When you bob the hammer, it removes mass which enables those lighter springs to accelerate the hammer faster than a stock hammer. It's all about force, acceleration and mass and a primer requires a sharp "strike" rather than a slow "push".
Think about it this way: Compare you (stock spring) pushing a motorcycle (stock hammer) to a kid (JP springs) pushing a bicycle (lightened hammer). You can both (for this instance) push your respective 2 wheeled vehicles at the same acceleration rate. If the kid (JP springs) were to try to push the motorcycle (stock hammer), it would accelerate much slower than them pushing the bicycle (lightened hammer).
Does that analogy make sense?
Well, being an engineer, I'm the kind of guy that wants to measure mass, spring constants, hammer acceleration, and resultant force of primer strikes, but really, if you all have empirical evidence that this works well (and I've no doubt that you do) then that's the most important thing.