I would have suggested an increase to 0.25u. That would have been more than doubling your previous dose. In addition, if a reduction doesn't hold, you increase to the last good dose.
Given that Magellan is a long term diabetic, you use below 40 as your reduction point. Alternatively, if he drops below 50 on 3 separate cycles, you can also reduce. I may have missed if your kitty met either of those criteria when you reduced the dose last week.
You may also want to consider evaluating Magellan's dose every 6 cycles. It looks to me like you're holding the doses for longer than is really necessary. It's often more difficult to get a cat into remission a second time. You may need to stick to the TR guidelines more closely to get the numbers back down.