About this 3D model
This is similar to one of my old arduino mounts, but it's just a touch nicer. Warning - I find that when I slice this it sometimes ends up with a layer printed right through the small mount holes - I just poke through this with a screwdriver or needlenose when it happens. The second one *should* be a slightly better fit for the arduino - I moved the top hole that mounts to the MM frame up one MM, because I found it impacted with some arduinos. I also moved the top left arduino mount hole down .5mm, because I found it was possible to use it, but that one hole seemed slightly out of place.