brad, i saw your post from yesterday but didn't get a comment put on it.
are you feeding him whenever he is hungry, or are you trying to keep it at specific times?
with a cat in high numbers, they don't metabolize their food and they will be starving. when you feed him, however, it would be best to keep a majority of his food in the first part of each cycle so the insulin is there to deal with the carbs. for cats who eat little, many of them can graze. when i stopped feeding punkin at +6 and +9, his numbers got a lot better.
i wouldn't necessarily reduce the total volume of food you are giving him, because we don't want him to lose weight, but can you give it to him mostly from the time of the shot and for the first 4-5 hours after that? see if that doesn't improve his numbers. and always pick up the food so he isn't eating anything in the 2 hours before each preshot test.
also, keep on the every 6 shots increase so we can see if we can get on top of these numbers. that assumes you are getting a mid-cycle test and preshot test in every cycle and the nadirs remain above 200.
are you already doing all of that, or is any of it a change?