Thanks for the comments!

I got to go for a short ride last night, and this setup actually works real well. The shift onto the 42 is a bit slow, but not too bad. I am leaving this morning for NV to go ride Bootleg Canyon and Red Rock. That will be the real test for this setup!

A 36t would probably be a better starting point that the 34t that i used, but I didnt have one. And is there such a thing as a 36t for an 8spd?

I am curious if the narrower 9 speed components would like something like this. Seems like the tolerances would be too close.

Interesting idea about the CNC shop, I may have to consider that at some point...