I increased the size to match a more Creality size they also use an M4 nylock the nut is embedded with a pause at layer 30. This allows you to change both the color of the filament for the text to read better and it allows you to set the nut in place, it's a tight fit but it will fit if your printer is calibrated. I have already tested and printed one and will be making about 12 of these so they will be put into use on my machines. 

You really should do this in ABS/ASA if you can but PETG will work just make sure you have your settings right.