I used the following sizes for the STL files:Max length: 7 inchesMax width: 2-3/4 inchesMin wheel spacing: 1-3/4 inchesMin wheel clearance: 3/8 inchMy printer (UP! Plus 2 - Afinia H480) has a print bed of about 140 mm, so the pictures and truncated STL have the corners removed so that it fit diagonally.
I am a firmware engineer, but my education is in mechanical engineering. I particularly like to work on projects that involve electronics, firmware, and mechanical hardware. And cupcakes.