True, acromegaly and gigantism have dollops of GH dumped on them, but it's still not such a great idea to mess with it in any way unless you absolutely have to.
If you've ever seen animal studies that plot hormone concentrations versus time, you'll notice that it's this spikey mess that can easily get thrown off by any number of factors. Having said that, I think it would be hard for any one to truly say that there are any "safe" levels since baseline hormone concentrations are different in everyone and only known after a week(or month) of extensive sample collection and lab work.
After a while, you appreciate just how delicate a biochemical balance we all walk and you try not to take that for granted. However, if you're feeling lucky and/or experimental then who can stop you?
Oh, and FYI, what you probably want is IGF-1. GH is just the middle man.