Hi Rowland
The trick with the DSS may be useful for people who don't run linux. Tricking DSS worked (and DSS complained about the lack of bias files in the last step) but I am not sure if it did the right thing.
Anyway, my problem with the master TIFF files created by your script was debayering before stacking. DSS will not debayer TIFF files (at least I could not get it to do it).
I tried Regim a few days ago and liked it a lot (thank you for the hint

). More linux programs will make my life easier :-)
Regim will debayer TIFF files but, as far as I could see, it will only do one file at a time (menu Color -> RAW debayering). Ticking "Files are RAW" in Preprocessing -> calibration works only for RAW files, TIFF files were not debayered. I will check the forum you mentioned.
How are you actually debayering files from your DSLR? Am I missing an option in Regim (very likely).
Again thank you
Luka