Merlin is on a 13/11 or 12.5/11.5 schedule. Currently, Merlin is on the later. You can use this type of schedule when you are on an "in and out" type insulin like Prozinc. So, once you have plenty of data, you may start to see a pattern that one of your pre-shot numbers, the majority of the time, is higher than the other. For example, Merlin's AMPS are generally high and his PMPS are low. So in order to balance it out a little or catch the AM shot before it gets too high, I shorten the time to shoot; hence the 11.5 or 11 hours between shots at night. Prior to this new schedule, we were even having discussion on this site to try shooting TID. Ugh, I really didn't want to do that. Prozinc typically lasts 12 hours but for some reason, Merlin's shots lasts longer in the day and shorter in the night. A great example is when I was gone for two months starting in March through April. You can easily see his high numbers in the AM. He was on a 12 hour schedule during that time. I believe that most cats do very well with a 12 hour schedule. Oh, and you asked about if the sliding scale is used due to a 13/11 schedule....no it is not. Sliding scales can be used with a 12 hour schedule.
When Merlin was first dx, I did find that consistent dosing helped with his bouncing. Merlin would bounce for days and eventually, his bounces started to decrease both with time and intensity. Today, he hardly ever bounces and when he does (usually from a very low number), it is only for that next shot. So for him, the sliding scale works very well. My goal is to get to a safe, green number with each cycle. It really takes a lot of time to hone in on a successful, sliding scale, i.e. there is a lot of adjustment that goes on. The success of a sliding scale is knowing what his low number will be with any given dose, so sometimes in order to know that, consistent dosing helps you understand that number and dose.
In order to figure out a proper dose with Prozinc, you need to know the AMPS number, PMPS number and nadir. There is no way to figure out a dose based on one test per day. That is why I asked if you couldn't get some mid-cycle tests along with your AMPS and PMPS numbers for you 1u dose. Without that combination, it is impossible to figure out what the dose should be. It is hard to suggest a dose when one of those key tests are not available and it is hard to suggest a dose for a sliding scale when there is only a few days of those key elements. When ever I have a new dose that I am giving, I always make sure that I can check at least at +4 to see where that new dose is taking him.
You still may want to consider a 12 hour schedule and maybe 3-4 cycles of consistent dosing (unless Andy throws you a weird number) just to see where that dose gets you at nadir and within that 12 hours. That way you can test at +10 or +11 to see when the insulin is wearing off just like BJM suggested. You may find that you do not have to change your 12 hour schedule. If you decide to go to a sliding scale, testing at AM, PM and nadir will be crucial for you in creating one. Periodically, I go back and re-read the Prozinc protocol just to make sure that I am making decisions based on that proven information. Along with the awesome folks here and the protocol, it has helped me and Merlin immensely.
Again, you are so awesome for bringing Andy into your home. Andy is a very lucky boy. Also, great job in your testing and all your questions. Hope this info helps and holler if you have more questions.