For some reason, vets must get a talk when they're in school that causes them to be anti-home testing. (Either that, or they figure they can make big $$$ by having you bring your cat in to be tested or have a curve done.) Next time your vet gets on this particular soapbox, ask how many times they test if you were to bring Moo in for a curve. (They test every 2 hours.) The notion that testing stresses out a cat seems to have taken on the stature of an urban legend with vets. I think if you were to poll people here, you'd find a very different perspective. However, when a stranger -- the vet or a vet tech -- is poking a cat, I would have no doubt that the cat is stressed. For example, I could probably hang Gabby upside down by her toes and she'd put up with it. If my cat sitter were to try to test Gabby, either she'd lose a finger or Gabby would hide. Gabby doesn't like strangers -- even strangers with food! Keep in mind, BG tests at the vet's office reflect stress. At home, they don't. Your vet is basing her conclusion that cat's get stressed with testing based on a biased set of data.
If you go back to the journal article on the Tight Regulation Protocol, if a cat drops below 50, the dose is reduced. In other words, a cat's BG MUST drop into lower ranges for the dose reduction. It's expected. It doesn't mean that Moo is having a poor response to Lantus. Please keep in mind that in order for the study to be conducted and for the article to be published, it had to pass an ethics review at Dr. Rand's university. In other words, that drop into lower ranges is safe if you are following the principles of tight regulation.
This is my long winded way of suggesting your vet has not read the TR protocol. If you'd like to share the article with her, I'm attaching it. That way your vet won't think your listening to a crazy bunch of cat ladies. Rather, we may be crazy but we read the research so at least we're well informed crazy cat ladies.