There is a huge misconception between slouching and hunched.
Hunched position mode been used since the days of Buddy Rich and so on.
Slouched is when you at the dinner table and your mommy hits you over the head and says, "Straighten up you back, you look like your father."
This only creates a sense of a complex in your life. To always be concerned about what you look like to others, instead of just have fun in life and being creative.
Look at Einstein for example, he invented the Afro, or he just didn't have the money to buy a comb.
Lets not get out of focus about posture and enjoy drumming no matter what you look like. Besides, no one can see you sitting behind the skins. We all get old and eventually end up slouching anyway. So why fight it.
You can be more concerned about your posture and create a complex or you can just enjoy drumming the way it is.