Sandisk Extreme Pro and USB port mapping - don't make the same mistake as me!

Okay, so don't use the Sandisk Extreme Pro USB 3.1 drives for the discovery phase of the USB mapping! It turns out that if USB2 is disabled on the port then these drives don't work at all, and therefore don't show up in your SS ports. I used a USB3 hub instead and it worked fine.

Wasted a good 4 hours of my life on this though!