I have made Z-couplers and all the other stuff here to solve the Z-wobble problems. It changed a little but it was not a solution of this problem. In black despair I have made stability improvements of the gantry. see the before-after photos. blue is before, red is after this changes. (ABS, vaporized) 1) holder of the Z-rod. This rod is moved around the right z-profile. [zrod_r.scad] 3) M5 rod between 1) and corner of frame 2) holder for Z-axis linear bearing [zbar.scad] 4) piece of sheetmetal for stability of Z-frame, both sides. 5) same as 1) at lower position [zrod_r2.scad] without photo: left side diagonal M5 rod. [zrod_l.scad] Now there is 20mm more X workspace. If you will use this feature, change in the firmware is required. 2015/01/25 update: bugfix in left side 10mm rod holder