That is a little low for a +4, but hopefully nothing to worry about. By now you have probably already gotten past nadir and any real danger of low #s, so I hope it all went well! It's always good to have the Hypo post from Health handy somewhere for reference - it has good info on what #s to worry about, and what to do if you see different #s, symptoms, etc. I have found it invaluable in a crisis (or perceived crisis, not sure I've ever really had a true crisis - Bix has been in hypo #s before, but his body has taken care of it better than I have!).
I would probably go back to the skinny 1U I guess. Sometimes a lower +4 like that can be a good sign that their body is kicking in and getting them to good #s, but it can also be the dose too high, and if you aren't around to monitor, probably safer to shoot on the light side. *sigh* because I didn't like those yellow nadirs the past couple cycles, but what can you do. I'm not usually a big fan of letting the dose "settle" as that wasn't my experience, but I haven't used ProZinc so perhaps my POV would be different if I had. Since others are getting good results with it, I'd go with what they are recommending.
As far as shooting a different dose AM vs. PM yes it can be done, but I agree I would hold off on that at this point. I think it makes it more confusing to know what is going on with a dose, and it can cause more problems than it solves. It seems most useful to me for a cat that has clear & predictable patterns, and is expected to be on insulin for a while (lifers, that is). If the cat's response is variable like Squishy's is, and there's reasonable hope of things improving quite a bit in the near future :mrgreen: then it seems to me it would just confuse things (compounded by responses like tonights, which leave one wondering what dose would be the right one to shoot).
If you did want to pursue it, I would try a slightly higher dose in the AM than in the PM, counter to what would be intuitive from shooting just based on PSs (i.e. higher dose at night for the higher PS). Higher dose in the AM might lead to better duration, and lower PS at night, lower dose in the PM might even out things by letting the AM PS equalize a bit more with the PM one. Short version then is I wouldn't recommend it, since shooting a higher dose in the AM seems a little scary with the lower PS, and shooting a lower dose at night to let the AM PS get a little higher seem counter-productive. Anyhow, it's probably all an aside for now.
Hope the rest of your night is going well and you are able to get some sleep. If you get into any real crisis & no one is here, be sure to post on Health to get faster responses.