Mount Rotary Encoder E38S6G5 adjustable fixed parametric

I'm building a hand-cranked organ with MIDI using software that includes a speed counter for the crank shaft. The software designer's chosen device to count the revolutions is the widely available E38S6G5, which has a single physical size but lots of options for the number of pulses per revolution. 

My organ will be using a standard GT2 timing belt to drive the encoder. These belts are available in a range of loop lengths. I need a way to adjust the belt tension to suit whatever loop size I end up with, so this model's default option makes the mount with a slot for one of the mounting bolts and a fixed point for the other. Changing a single parameter in the OpenSCAD file will make a mount with two fixed holes. (I've 3D-printed only the mount with slot that I need so don't have a photo of a mount with two fixed holes.)

All the design parameters can be adjusted in the OpenSCAD file. I suspect your faceplate mounting screw holes may be offset differently to mine. To get my mounting screw holes in the right place I printed (on paper) a protractor, cut that to fit over the encoder and read off the angle to the first mounting hole from the cable entry. Mine was -15 degrees which is the value in “hole_offset” in the OpenSCAD file. (A value + or - will work here.)

I've provided .3mf files for both styles of mount (fixed or adjustable). These have the model cut into two parts with holes and studs to align the 2 parts correctly. My printed model is stuck together with superglue and seems to be perfectly solid. The .stl files are for the same models, but will not simply print as they are.