I'm quite new to chdk, but it seems I've understood the main features, and it's very useful!
I'm experiencing a problem with noise reduction at high ISO. I'd like to always disable the dark subtraction, also with long exposures. This works fine, but if I try to increase the ISO setting above 3200 ISO (2000 true, setting 20 and 100x multiplier) the noise reduction is automatically done even if it is disabled.
I tried also with a script with the same results.
My camera: Canon IXUS 220 HS (also named Powershot ELPH 300 HS)