Unfortunately to do the same with ardupilot software ( APM/Pixhawk/Pixracer) it is a bit more complicated.
The set-up for the switch sets up the switching points at roughly equal points on the scale 1000-2000 us.
The APM switch ranges are fixed (unlike CF/BF)and furthermore are not scaled evenly.This is from the Wiki:
"If you want to support 6 modes then the transmitter will need to emit PWM widths of around 1165, 1295, 1425, 1555, 1685, and 1815 milliseconds."
In addition you must use Channel 5
How It's done:
The standard calibration for the switch sets up the switching points at roughly equal points on the scale 1000-2000 us.
The APM switch ranges are fixed (unlike CF/BF)and furthermore are not scaled evenly.
Therefore the positions do not correspond.
I found the easiest way was to use a curve to shift the positions, the curve I used was
CV9 ( A 9 Point Curve )
-78
-56
-32
-22
-5
15
31
48
81
I calibrated the 6 pos switch as normal then applied the curve this gave me :
Position1 1108,
Position2 1306,
Position3 1431,
Position4 1585,
Position5 1708,
Position6 1911,
Close enough for Government work
I could have messed around with the curve to get it a bit closer. But it works and I'm lazy 
Painless360 has a video on the 6-pos switch in a Taranis that uses a 6 position curve but the principle is the same, and it explains the problem a bit better.
Hope this helps
