I have the same issue. Including the ability to allow users to set an additional offset input value to adjust the calibration just makes more sense than spending endless development hours trying to improve a complicated process. Clearly many users have this same issue.
My calibration is off by about 100 pixels on y no matter what I do, otherwise it would work perfectly. This isn’t a game developer issue, this is the Tobii application showing me that it’s not calibrated properly.