Fan duct and Mini Differential IR sensor mount for E3Dv6 hot end with commonly used mounting plate

I made the original fan duct to fit a delta - but then I decided that I didn't like deltas! I then made some modifications so that it would fit my existing Prusa i3 and a new recently built CoreXY.

This meant changing the mounting plate from "Kossel effector" to "standard 50mm spaced M4 holes", as found under a Gregs' Wade Extruder (and also used on many printers). I also increased the diameter of the fan hole slightly to reduce air resistance.

The main reason for using this mount is that