I think that the people worrying baout their natural GH are wasting their time as the GH that you inject will shut down your natural production anyway, if it's not shut down already (the older you get the less GH you produce).
I found that results are the same no matter when you inject. I personally like an injection before bed because when I wake up all the obvious GH effects are greatly obvious in the mirror (glowing skin, denser looking muscles, etc)
When I use insulin as well, I take 1/2 of my GH with the morning insulin shot and the other 1/2 before bed.
Also, GH doesn't convert into IGF-1 but it makes the liver release IGF-1.