After calibrating the max speeds of the stepper motors, the first test print was an encoder mount that allows the RepRap magnetic rotary encoder board v1.0 to clamp onto the extruder drive motor
There are recessed spaces for a #4-40 screw and nut so the part can be clamped around the motor body. With this mount, the board is positioned exactly so the AS5040 chip is directly over the rear drive shaft. A small magnet is then attached to the rear drive shaft. (Note: These pictures display an earlier version of this part without its 4 mounting screw holes in the top for the board. The last picture in this post shows the board mounted into the final version of the part with the 4 screw mounting holes.)
The first layer is yellow because that was what color was in the heater barrel before I put the natural colored plastic in.
It fits quite securely, and the part has a nice surface finish as well. Now the the tricky part is getting it to work with the extruder board firmware. (The above image shows the encoder board before any components were soldered.)