Hi there! I have to agree with the others that a 33 is a bit on the low side for a kitty that is getting insulin and it certainly means a dose decrease, but by what I am reading in your responses, that is not going to happen, so I can only suggest that you keep those two good eyes on Mr. Barney for signs of hypo!
Out of couriosity, what type of food are you feeding Mr. B? My kitties used to get wet food 2x day w/dry kibble for free feeding. When Spot was dx'd the kibble was d/c (except for civvie Ali, which is another story), and the lower carb wet food was fed. My civvie Ralph was overweight...19 lbs of pure kitty. After the diet change, he dropped to 16 lbs. He gets 1/2 can Sophistacat in the a.m. and p.m. and for his evening snack he gets a small handfull of kibble (under my watchful eye so that Mr. Spot doesn't get any). He also gets some fishy flakes in between. He has maintained his weight. So, maybe just a change in food would help with the weight loss.