Hi Adam. Welcome to the obsession, er...hobby, of boas! lol
I generally pick up babies regardless if they are hissing or not - or even striking. If you pick the little one up and it hisses, continue to gently handle it for a few minutes, I've found most hissers will calm down once outside the cage. If it hisses or strikes and you immediately put it back, it learns that is the way to teach YOU to leave it alone. If it strikes or hisses while handling it, handle it for just a few minutes more, then put it back (that way it doesn't associate the hiss or strike with being placed back in its cage). BTW, in handling what I've found to work best is to simply support the snake but not restrain it...many otherwise gentle snakes will become quite testy if they are forcibly restrained and more likely to strike. I simply support my guys & gals in my hands or arms (or lap for the bigger ones) and let them move around, gently offering support the whole time. For those that I don't trust around my face, I just keep gently pushing their heads away with a finger or hand when they come towards my face. FWIW, in regards to bites, I've been bitten by several of my snakes over the years and it isn't that bad (and I'm a whimp, I don't like pain! lol). Even my 6 foot female bit me once a few years ago and you could hardly tell she'd bitten me by the next day. That bite was my own error, I startled her by just reaching into the tub she was in to pick her up without letting her know I was there first with a stroke along her back like I usually do. Live and learn! Raven