A couple of questions as i am designing my own build, using your ideas:

-so you believe 3kw spindle would be better than 2.2kw?
-how you did the oiling system? did you use the original nipples and modify them? why not grease? how much oil is used under operational condition? What oil?
-where did you get that spring shims that make the preload? what are the specifications? how did you calculate the distance between the 2 nuts , so that they would be mirroring each other exactly and the shims to fit in?