I can't bear the thought of hanging any camera around my neck straight down to chest/belly. I don't even do it with a Leica. Ewww, an awful way to carry a camera!

For me it's almost always over one shoulder then down diagonally across to the other side of my body... you know, like a seat belt. It's far safer for the camera, even with two, and FAR more tolerable for your neck. Provided you've let the strap out long enough you can quite easily and quickly bring it up to shoot with. If you're trying to be a little incognito, for want of another way to put it, you can easily tuck the camera away behind your back then stick your hands in your pockets and carry on whistling and acting cool & nonchalant If you've a big lens like an 80-200, you put it upside-down, more comfortable and reduces stress on the mount.

If I'd done it straight up-down all this time I would've had to consult a neurosurgeon long ago to repair some acquired cervical nerve damage - bugger that!!