in response to your PM:
Purrdy is looking great and yes, should be in a range to avoid organ damage most of the time. Most of us find that our cat's renal threshhold is somewhere around 200 or a little lower.
If remission is the goal, I would try to get him a little lower, though. Once they are this nice and flat, usually it's pretty easy to just add a bit more insulin to adjust their range down a little at a time. Probably he won't all of a sudden turn into a diver and bouncer. Once they are under about 120 all the time we often see a lot of healing taking place so there could be some fast dose reductions then, unless he decides to be really cooperative and just earn his reductions by surfing green for 7 days at a time. That's when OTJ is most likely to happen - after they are staying under 120 all the time.
His spreadsheet reminds me a little of Jazzy's. She was so consistently flat that it was actually very easy to manage her numbers, even when I couldn't test a lot.