There is no other car in the world that needs a lowering more than the MX-5 NC.  The tire to fender gap is just ridiculous:

Rumors says Mazda had to raise the suspension after the final design to conform to new safety regulations or gain an extra star in the NCAP rating.  
Even in full compression mid corner on track the car looks like a pirate ship:

The other problem is excessive body roll.  The car actually feels very nimble and controlled on track but the snap oversteer can be really scary as there is a lot of mass on top of a very high roll center that get tossed around. 

The solution is easy.  Adjustable coilovers.
I would have liked Öhlins DFV coilovers as my experience with them on the MSM was fantastic. 800lbs springs that rode better than stock, extremely good build quality, thorough instructions etc..   (The opposite of my first set of coilovers btw.)
But since I need to have the car road legal I need TüF certification  = KW variant 3 is currently the best option.

V3 got both rebound and compression adjustment. It lowers the car as much as 70 mm which is actually needed make it look like a sports car   The kit uses helper springs to ensure constant preload under full droop and uses the stock top mounts for a squeaky free ride. They are very well built and promises OEM like durability even in scandinavian salty winter roads. Shock body is SS so it is probably quite heavy compared to other aluminum.
The internet lists the spring rate to "230 lbs front, progressive rear" which sounds like a joke.  If it actually is 230 lbs springs there must be some other magic going on as it feels very firm and planted, even on the track. 

Assembled front shock/spring.

Installing was straight forward.  You can save yourself some work by supporting the rear shock with a jack while removing the top nut instead of using spring compressors. Beware, there are more preload on the NC OEM suspension than the NA/NB so just removing the rod nut will result in some serious carnage.
You need to remove some plastic covers to get to the compression settings as on the NB.

Here are some pics of the front suspension when supported by the car jack. This is not the same as when lowered on ground but still.  The A-arms are pointing upwards which is probably not optimal. Maybe the new revised lower roll-center ball joints on the 2009+ NC fixes some of this.

The end result: (sorry for the dirty car)

Front end is maybee a tad lower than what I like. I havent had any problems in normal use except for scraping the wind deflectors on very steep ramps. I might raise it 5-10mm.
I havent tried them on my local track yet but I did 20 laps around Nürburgring nordschleife. The stiffer and more controlled ride really changed the car.  Biggest change is out of corners where it is planted and more predictable. Cutting corners over curbs does not unsettle the car like with the stock SUV suspension.  I still got the stock 21mm sway so this is the next and final step.  I'm going for 25 or 27mm front and something that matches rear.
I'm very satisfied with the KW 3 but the real test will be on Rudskogen on R888.