MacMarty,
Great to see progress on your machine! The adjustment system you have for the rails is an excellent idea.
I'd like to help with your binding problem, but I'm not sure I understand exactly what the problem is you are seeing. Does the system slide smoothly without the ACME rod installed? Are you just seeing the screw bind? If so, this is most likely from a small misalignment that requries the screw to "flex" in the middle of the travel. Even 1/16" off can make everything bind, so you might need to readjust or even shim the 2x4's you have under your rails.
Or maybe you're just having trouble fitting the radial bearings on the ACME rod? Let me know -- I'd like to help.
Ahren
www.cncrouterparts.com