if increasing sensitivity doesn't help, you must tweak something the curves.
The vertical repressents the real head movement and the horzontal the ingame headmovement.In this curve of the x-axis you can see that if you move your head 45 degrees in real life, in game your head wil turn 180degrees.Just imagine what wil happen if freetrack loses track of your leds at 30 degrees......Ingame you can onlyturn your head 140 degrees.If you lower the most right point in that curve to 30 degrees on the vertical line instead of 45 you will see that you don't have to move your head so far anymore and can turn your head 180 degrees ingame.If you still have that problem after this , post a picture of your curves and profile setting.
cheers Stormrider