I just got my second black edition in the mail. Its the spec Q. I took the center diff out to confirm something I've noticed when building the kit. Now this may not bother some and I'm not saying its an "issue". However I am very anal as some say when I build/rebuild my stuff. Now I noticed this first in the white edition, and looked for the issue when building my first black edition. What ive noticed is the center diff doesnt spin (on my kits) nearly as free as it could. Now some people are gonna say b.s. blah blah blah. The thing is, this is a good thing. It means if you care the car could be juuussssst a hair better (smoother/more efficient). What I've noticed is the top half of the diff holder (really the middle, but top of the bearing holder) is the "issue". There's a tiny section (last pic) that isn't as big of an opening as the rest (almost oval). On my cars this is where ive measured the smallest diameter. Now the measurements say it should be good. However I cannot slide the bearing into its home. I did get one half on my 2nd BE that was fine. The bearing slid in perfectly. The smallest part of that bearing holder was 16.10mm with rest being entirely 16.15. What I've done is used my drill press with a tiny stone bit with 90 degree edges (there's a lip that keeps the diff in place by the bearing so be careful), on the lowest speed I've "messaged" the part and measured. Until I get the bearing to juuuuust slide in. After I've got it everything back together I can clearly see it spins much more free. And I know for a fact once I break the car in the bearings will free up even more. I think with some extra attention to detail this car has the potential to be one of the most fuel effecient cars. The angles on the center driveline are small and should be very efficient. I will eventually swap to metal sheilded bearings for a little less drag as well. Anyway your kits may be perfect. If so great! But the next time your in there you may just see if you can slide the bearings in. Thats the easiest way to know if they are getting crushed by the upper diff half. I hope this may help someone.