Ok, got it working on my regular profile now.
What you need to do is set the mouse axis in the SST software. The small grey arrow that appears when you hover the mouse over it, use that for mouse x to select x axis and the same for the y axis so they both look like they do in the pic below. You need to do that for all modes including any pinkie mode you use. Also, I don't have any fallback states on any of the modes I use on the SST software. You still also need mouse headlook set to on and the headlook axis mode set to accumulate.
Just don't forget to set a key/joystick button to enable headlook in the first place. Also, you will want to set another button to reset headlook to auto-centre it again rather than disabling/enabling it constantly. That way you should be able to leave it on all the time.