The standard Folger Kossel stepper mount is fine, and I have used it successfully for over a year, but I wanted a cleaner solution that would combine the bowden tube and cable braid, and provide better access to the extruder by mounting it one the lower rail. By combining the cable braid and bowden tube, there is less sag and catching of the cabling.
This bracket mounts the extruder with unimpeded access from the top, attached with two screws and drop-in t nuts to the top rail, and has a relief recess to rest the lower portion on the bottom 2020 rail.
A bracket to zip tie and secure the cable bundle from the arduino to the hotend is on the left hand side.
Designed to be the same thickness as the original perspex bracket so the hardware can be reused. I reoriented the extruder so that the bowden cable is on the same side as the stepper motor cable.