(On the image is the previous version, new version had the metal nuts hidden inside the plastic part). 

Material: PETG
3D Printer: FDM 3D printer, average print time 45 minutes
Slicer settings: 0.2mm layer height, 4 perimeters, 100% infill, no supports, pause in 5.2mm to insert the M5 nuts. (pause is set automatically in gcode).
Post processing instructions: Clean stringing, adjust the length of bolts and install.