Ok, I edited /etc/evtouch/config and changed the MaxY from 6998 to 3939 and restarted X/GDM but no luck - probably something to do with the d(x/y) numbers. But I rebooted and reran the calibration and this time it also detected the MaxY and apparently as a result also set the dy values much better... still not 100% accurate (few pixels off) but much better!
Ok, I edited /etc/evtouch/config and changed the MaxY from 6998 to 3939 and restarted X/GDM but no luck - probably something to do with the d(x/y) numbers. But I rebooted and reran the calibration and this time it also detected the MaxY and apparently as a result also set the dy values much better... still not 100% accurate (few pixels off) but much better!