Hey Jake, I don't anything about how these DIY systems go together.... Yours it the first I've looked at. A couple of things come to my mind... First maybe what are you milling? How ae you going to enclose all of the belts and such from chips and or dust. Reason I say is I would think there could be a friction issue that deals more with tension of the belts with reference to the other axis. If the Y axis has more tension (friction) it will take more torque to move a given distance. Will the control software compensate for this? I guess in real simple terms you have say two motors of equil power. Your X axis motor is installed in a tractor trailer and your Y axis installed in a Arial Atom. Which axis is going to get to that point in time faster?
Just a thought... I do tend to over think things...LOL
Looks good... goes without saying it has to be ridged....
Using CNC Masters Supra Knee Mill, 4 Axis vari speed. Bob Cad V-23, V26, Bob Art