Disappointed with the Z banding, I replaced the stock Z-rod with a TR8-1.5 lead screw but this did not completely fix the problem, and the top mount would no longer work to suspend the lead screw without purchasing two TR8-1.5 nuts. So, I decided to move the Z motor to the top. (Was relieved to see that Ichbinsnur had done this so knew I was on the right track). I could not use his hanging mount since the acrylic housing I already made is too close to the frame.
I printed a mount to hold a pillow bearing to which the lead screw is now mounted, and moved the Z motor to the top. Slots on the printed mount allow for perfect alignment of the bearing with the carriage mount. I was also able to reuse the original aluminum Z motor mount with no motor displacement as the lead screw turns. Since the lead screw is suspended from the pillow bearing mount, this decouples the Z motor from vertical (Z-axis) movement of the lead screw, separated by a flex coupler, and has solved the banding issue. I did have to make one adapter. The aluminum mounted delrin nut (purchased on ebay) attached to the carriage was too close to the carriage so I made a spacer from 1/4 inch aluminum plate. The slotted pillow bearing mount made for easy alignment of the carriage mount with the bearing mount.
To rewire the Z motor in its new position, I just used some of the excess ribbon cable left over from the original build, and a 4-wire connector scavenged from an old PC, then set #define INVERT_Z_DIR to true in Marlin and reflashed.
I did have to print a simple mount for the Z-stop since the original bracket is now located at the top.
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