i think it has more to do with carbing up and eating too much. not just eating too much before the show, but all the time. if you eat alot all of the time, which is what the bigger guys do, it stretches out the stomach.
also, there have been times, when the guts havent been as big as in the past. if that was the result of gh use, the guts would be the same size all the time, but guys like dennis james, gustavo, ronnie, jay, dillet, and even fux have shown up with a smaller gut that in a past contest while being almost as big.
also, guys like dexter, kevin, david henry, flex wheeler, gunter, all do their fare share of gh/insulin and dont have the guts. maybe its genetic or maybe they dont each as much.
it could be the gh and insulin. guys in the past didnt have the guts, but also guys werent as big on stage and in the offseason and werent eating as much.
besides, what in insulin would make the stomach to protude out? insulin is mostly a transport hormone. does it transport more nutrients into the stomach and make it stick out? possibly.
but then again, who knows. check out fux in BFTO 99. wow.