Thanks for the considered response and especially that ratio. I think the ATK recipe used a partial can of the SCM, which is pretty awkward.
Incidentally (not for your purposes, but for anyone intrigued by the SCM/No-machine method), I was at Walmart today and noticed a clearance cart - Everything under $2!. It had cans of Eagle brand chocolate-flavored SCM for $1.98. Had never seen that before. I bought three, but don't have any results yet as I've been doing other things. I hope they're going to eliminate an entire ingredient for my chocolate ice cream. Then again they were on clearance, so we'll see....
So, anyway, I thought that I'd be whipping up some cream soon, so why not steal a little bit for an experiment? I looked at my wife's sweeteners and came up with Sweet 'N Low, and two stevia based sweeteners (Stevia in the Raw and Equal Stevia Extract). I asked her if she wasn't using any of them and she said she wasn't using any of them. Ok, so I looked back and I believe you said that Stevia would be acceptable, if not for brand differences/variances related to taste/aftertaste issues. Well, I'll never be able to anticipate your personal taste and I anticipate any level of success would not be as good as the sugar for me. But it's about the texture, right?
Alright, so gosh, I wonder if anyone has made SCM using Stevia. I found this recipe...
https://myreecipes.wordpress.com/2010/03/27/stevia-sweetened-condensed-milk/
Not only does she claim that it was a success, but the ice cream she made with it was 'amazing' Hmm. I'll just need some powdered milk. I think I have some powdered buttermilk somewhere. That ought to do....
Edit for a note about the temperature issue - I put my mixture in a 32oz deli container which fits nicely in the door of the freezer. So that's where it stays and it's probably decidedly warmer than if I put it in the back of the freezer.