Never used insulin, but it really does seem like what hurts guys while using insulin is eating too much food/carbs/sugar in order to "cover" the insulin as they are terrified of going hypo.
The other thing I've observed with guys who got fatter using insulin is that the vast majority of these guys are not lean in the first place. I think that the fatter you are, the less using exogenous insulin will benefit you. Just my opinion though..
Plus, most bodybuilders tend to be impatient and they jump right into higher doses of insulin and they adjust their carb intake to the amount of insulin they're using when it really should be the other way around.
I know he's just one guy, but Milos has probably used more insulin than anyone in the history of bodybuilding, and Milos not only has never had any distention issues, but he looks amazing for his age.
Milos has even gone as far as saying that he feels like there is no point in training if you're not using insulin.