Those are some very good questions that I'd like to know also.

I've been doing searches trying to just find a lower spring weight for the M&P9C as an option for shooting minor 9mm reloads reliably. I don't own a M&P9C yet, but I tried one with an X-Grip a few weeks ago and really liked it. One locally just came up two days ago with only 50 rounds fired for $400, but had to pass because really want an option for a lower spring weight like you get with the M&P9 full size (4.25) or 5" long or Pro models. If S&W or an aftermarket company comes out with a dual spring option, that would be even better.