I agree that, as long as KJ has control over the stories, it's in his hands how he wants it to play out.

I have to wonder about "747". In it, David seemed to have an influence on the Hulk-out, by slowing it down. In that sense, not to contadict KJ, since he is the "Master", there is a connection between David's conscious thought and the Hulk-out. There's no way to know for sure, but if the problems with the plane had resolved itself, David might have, at the very least, been able to slow it down even more. I think David's control over the Hulk-out was hindered by the fact that the Hulk's strength was needed.