Finally, I found a real mid year mechanical change. My wife and I both drive 2016 fiST's. Mine was a Dec '15 build and hers was built July '16. After measuring, hers has a 21mm front bar and mine has the 19mm bar. Suspension was "softened" says some posts around here but I can't tell much, even back to back driving it's still close. It's hard to tell them apart. You really have to take turns near the limit and even then it's not always apparent. My vote is it's an improvement all be it a very small one. She got it not long ago, I'll report back once I get more seat time in. Can you imagine.... she always wants to drive it!
Reporting back 5,000 miles later. I can tell hers (late 16) is a little softer and rotates more with less effort. While different when driven back to back, it is possible to tell. However, I doubt test driving two a week apart would show the difference.