Hi @enrico, many of the Tobii Pro range of eye trackers offer higher rates of frequency of eye tracking, customer calibration planes and access to raw unfiltered data so if premium accuracy is required then I would indeed recommend you considering these devices for your needs.
Please also bear in the mind that if you intend to use the eye coordinates for long term storage via the Interaction API then you will still need to acquire a special licence to do so as storage of gaze data is prohibited by the Core SDK Licence agreement.
In reference to the Z-coordinate issue, I have not been able to verify, but have passed on your comments to the developers and perhaps they will come back with some useful feedback for you.
Certainly, there is no option within the Core SDK for ‘extra accuracy’ but it may be worth looking at the different levels of filtering that can be applied to supplied gaze data which could affect the results you are trying to achieve. May I ask if you also got an answer from Sales yet as well and so got all the answers you need? Thanks.