Duet Mount for 15mm and 20mm extrusions

I designed this mount so it can work with both 15mm and 20mm extrusions so virtually any Kossel variant can use it. Rather than mounting on the Z tower, this one mounts on one of the lower base cross pieces. This keeps it out of the way - a nice feature if you transport your printer to events. My Smoothie mount (posted on Thingiverse) is mounted on the back tower of my Mini Kossel and I'm always bumping it into things!