If you take a look at my SS, Carter was only on Vetsulin for a few weeks - no time to really achieve regulation, so I adjusted his dose on a daily basis to a comfortable number to shoot in order to get SOME insulin into him while I waited for my Lantus prescription to be shipped and arrive. I tested him at his nadir, but when I first started testing, I didn't test NEARLY as much as I did later on... kind of became a testaholic. Which, Carter is super easy-going, so he didn't care about the tests!
Keeping him on one dose to do a curve, in my opinion, would still you allow test as much as you feel the need to. You're just gathering data, even if you didn't change the dose. However, if the vet wants you to keep him on one dose for 2 weeks straight and advises you not to test at all (which is dangerous in itself) 5.5 units is very high, especially for Vetsulin. For Carter, I did notice Vetsulin usually worked the same for Carter whether I gave him 4 units, or 2 units or 1 unit. The PS numbers were always high, so the actual amount of insulin made no difference in the duration of the insulin, but depending on the dose, his nadir would sometimes be lower.
I'm not sure if you've done the math already, so again sorry for any repeat information, but how much are you spending on Vetsulin? My bottle was $50 dollars, for example. So that's $50 dollars a month for a vile that will likely lose potency before you use the last drop. If you get an RX for Lantus or Levemir, you can buy a 5-pack of pens for around $170 with shipping from Mark's Marine Pharmacy. So yes, you'd be paying more upfront - but these pens will last you upwards of a year. So $170/12 months equals about $14.00 every month as opposed to $50. Vetsulin can work for some cats, but it appears that Dennis isn't responding as well to the faster-acting insulins.
I feel you about the money. At the time, I was unemployed and I got a small loan out in order to afford to buy the Lantus upfront - but I'm really glad I did, because Carter eventually went OTJ and has been in remission for 3 months now. ECID but I ended up saving so much more in the long run. I hadn't had him on Vetsulin for very long, but in my gut I knew he wasn't going to respond very well to it based on the data I already had.
Some people sell individual Lantus/Levemir pens on the Supply Closet for around $30 dollars. I actually some extra unopened pens myself. Just my 2 cents!