Hi @sgmrock, thanks for your query. Although it should not make a great deal of difference, ideally you would keep your head straight and move the eyes however judging by the setup you described, it seems most likely the problem is that you are mounted offset from that which the tracker is designed to operate with.
As you mentioned, the curved screen setup is not officially supported, but have tried using the ‘improve calibration’ setup from within the Tobii System Tray Icon? This might help improve problematic areas as much as possible with your current configuration.
It could also be worth checking if there are any strong sources of IR light (spotlights, open windows) that may lie close or in front of the eye tracker.
Hopefully some of this advice will prove helpful for improving your eye tracking experience!