Already taken into account fitment for all E9X models. Measured a ton of cars for fitment already. The only thing that changes is bolt hole configurations for all E9X. I won't know for sure if it will work though until my second prototype is done production and then I can actually get it installed on various models.
Might not work on the Mtech bumper with the OEM diffuser if the bolt holes aren't there. It needs something to be anchored on. I'll need to look at several cars with the M-Tech package and diffuser to know for sure how to mount it on but from what I've seen, it looks as though the anchor point has been deleted (might be due to the way some people are installing it? Not sure on that...)
Big difference is 335 vs non-335. LCI and non-LCI have the same bolt configuration so fitment will work regardless of LCI or non-LCI. The current design has three main sections: center plate and side plate for a total of 8 fins. The location of the non-turbo pipes means only the center plate with 4 fins can be used. The two biggest fins are located on the center plate anyway and if it's for cosmetic purposes, the center plate fins are the most noticible.
I've designed two variations for the fins too - one to work with the CF deflector and one to work without it.
Lots of hours spent doing the design!
As for testing the function, I'll need to set up a set of load cells under the tires in a wind tunnel. Might be overly costly at this point unfortunately so I don't think I can get any numbers to show what kind of downforce I might be able to generate. Also, depending on the overall ride height, the downforce would change.