I have one I use for my travel camera. You don't take it off... just slide it round from your back to front and unzip the flap to grab something out. I think it works as I don't overload it with a lens in every available posi. The 200 (and I think 300) also have a stabilizer strap that comes around the other side of you to keep it on your back whilst keeping both hands free whilst rock hopping, etc