Hi Lee,
Interesting results indeed.
I would be careful though when comparing StDev for the entire images and using it as a measure of noise. Dark subtracted image will have lower mean ADU value, and that could affect the StDev? Perhaps instead of comparing StDev for the entire images, pick a smallish area with background only, if possible, and check StDev for this area in both images.
Anyway, whatever technique works and if you are ending up with cleaner images, that's great
