Hi,
Yes I agree. There needs to be a universal calibration method. The best way would be for a first time run to calibrate and self-flash the value on a known address. Maybe at the top of the flash space. On subsequent power-on events, if the values exists in flash memory, no calibration would be required(touch four corners).
(It looks like we can use the EEPROM area for what we want) http://www.arduino.cc/en/Reference/EEPROM
To store the results of the initial calibration test.
I have been busy with holidays, family, and I sneek some Arduino time in when possible. Also trying to teach myself clojure.
Thanks,
Ed Diaz