None of the rolls I've developed thus far were "important" per se, but they weren't serious tests either as they'd been shot over a few months under varying conditions (and purposefully used different films because since I'm used to only developing b/w it's intriguing to me that times are all the same in C-41).

hrst, I'll try the water practice as a test, thanks! Water bath is around 110 or so and I do leave the thermometer in the bottle of developer until it has normalized on 100F for a couple minutes (it's the kind with a round dial face and a pin sticking straight down, so I can just leave it propped in there until ready). I think the process of heating/measuring is correct, but it's possible this thermometer is no longer accurate.

Keith, by "temp drift" you simply mean that the tank wasn't truly staying at 100F for the whole 3:15 minutes, right? Are you suggesting to stick the thermometer in between agitations to keep an eye on it? (although once the temperature drops it seems like it's too late to fix, developing time is so short).

I do suspect the times a bit as well, because it's hard to figure out exactly when to start the clock when pouring developer in, and am I supposed to match the very last drop of developer coming out of the tank with the timer beep? And in the few seconds it takes to get the blix poured in, is the film continuing to develop? Maybe it's just my b/w mind thinking but extension of time in this sense seems like it would simply lead to overdeveloping (increased contrast, grain, exposure) but not necessarily color casts.

Anyway, the test of cutting up a roll sounds like a good one...might shoot a cheap one tomorrow morning to play with.

Just to add: in addition to reading here and the manual, I followed instructions from someone on Flickr whose only deviation from my materials is that he uses glass bottles. Everything else he uses is the same--kitchen sink as a water bath, Paterson reels/tank, Tetenal. That's what initially made me believe this would be easy .