About reason I picked Nema23: just I had 3 pcs for free with L-brackets from some old med equipment)). They are smallest in Nema23 series, but you know, they not so bad ), they stay cold all the time and torque are quite good than Nema17.
I added 8mm version of middle part for you, and I'll add the bottom part for Nema17 motors soon... Other parts is the same, just rod mounts would changed on SK8.
With 10mm guides design is less prone to twisting - 8mm will require additional reinforcing structures connecting the upper and lower panels. I don't tested that kind of modification (even haven't printed this parts) and you'll assemble it on your own risk.
About plans to realise design files - tell me part you want and I'll send it to you by email (SolidWorks 2013).