Hud F18, the display on the hud is moving and not fixed with tobii eyetracker

I am using tobiie eeye tracker. If i am flying with th Asobo f18 and look at the display on my hud and keep my head still the image is complete visible. As soon as i move my head forward that means tobii eyetracker will zoom in for the complete monitor screen what is correct but the display on the hud is also zooming in what means that the speed and altitude indicators might disappear for a bit or completely, depending how far I want to zoom in. Also if I move my head a little bit to the right or to the left the display on the hud is also moving to the side so I cant see only one of the indicators altitude or speed. The rest disappear. I dont use the option to see the hud display in my helmet and that is on zero. If i watch youtube videos from the f18 also with people who use tobii eyetraceker the display on the hud is fix and not moving. How can i make it work that the display on the hud is fixed and not moving what I see on youtube?
If i turn tbe brightness up the display will move with my head as a helmet hud, but I want the display fixed on the hud, maybe somebody knows a solution?