Hi, Elinor. I'm not sure I've stopped by before today.
A couple of thoughts for you to consider....
Generally, if you get a low number toward the end of the cycle, it's still helpful to test at your usual pre-shot time. There's a phenomenon called a "double dip" -- numbers drop again after nadir and close to pre-shot time. I'm not sure anyone really knows why, but it does happen. (It's probably our cats doing their jobs and confusing us!)
With TR, you want to get used to the idea of shooting low numbers. Most of us, as we gain experience, will shoot anything above 50. I wouldn't recommend you do this now. Rather, give some thought to what number you would feel comfortable shooting and gradually get used to shooting progressively lower numbers. You want to have a feel for how Sibon responds to lower numbers and whether his cycle begins to flatten out. While it's counterintuitive, with Lantus, shooting low often produces a low, flat cycle versus causing numbers to plummet.
The advice your vet provided is pretty consistent with what many people hear from their vets. Most vets don't have very many people who will home test or who become knowledgeable about how to steer low numbers with food in order to keep their kitty safe. As a result, they tend to keep cats in higher BG ranges and discourage shooting low. This makes sense if someone doesn't home test. With Tight Regulation, the goal is to keep your cat in normal BG numbers (or get into remission) and it's very hard to do that based on letting your cat sit in higher numbers or not shoot below 180.
I believe what Kris was suggesting is that you're dealing with 2 factors that are influencing Sibon's numbers this morning. When you skip a shot, most of the time, the numbers will be high by the next shot time. (Sometimes, this doesn't happen due to the depot kicking in and keeping numbers level.) In addition, with the drop into the "green" zone, it's very likely you're seeing a bounce. With a bounce, a cat's body reacts to low numbers, a fast drop in numbers, or a drop into numbers the cat's body isn't used to by causing the liver and pancreas to release a stored form of glucose along with counterregulatory hormones. These cause numbers to spike upward as a naturally occurring safety measure. It's annoying but normal.
If you are following TR, you want to evaluate Sibon's dose every 3 days/6 cycles. If his nadir is largely above 200, you increase the dose by 0.25u after 3 days. If nadirs are mostly under 200, you hold the dose for 5 days and then evaluate if the dose is bringing your cat into normal numbers. That said, because you skipped and there is likely a bounce in play, you can wait to see what Sibon's numbers look like once the bounce has cleared. My best guess (and it's a guess) is that Sibon's nadirs are likely in the high blues/low yellows.
If this were my cat, I'd probably increase the dose but I've had years of experience at dealing with low numbers so what works for me may not work for you. Generally, with TR, we tell members who are new to FD to post and ask for help if you get a pre-shot that is under 150. If you are nervous about numbers in that range occurring during the week, I don't know if reducing the dose to 1.0u is the greatest idea. If you feel the need to reduce the dose so you are reliably shooting twice a day, I'd give some thought to reducing the dose to 1.25u (a 0.25u reduction).
If I were totally in your shoes, probably not. You have a fair amount of data, but you shouldn't shoot a number if you are uncomfortable doing so. The trick is to gradually decrease your "no shot" number - push your comfort zone a little. So your "no shot" number has been 180. How about you lower it to 150, assuming you have all the supplies you need and can test. Then, once you are comfortable with that, you can lower it to 120, etc. Data is your friend. The more you have, the better idea you have of what the insulin is doing.