I second the Black Rapid. I have one, and it is a lot more comfortable than a standard strap. You can set it up so the camera and lens line up in the small of your back, protected and out of the way when not shooting. All you have to do is grab the camera and slide it up to your eye. Well worth the money.
Have you tried turning the strap-and-camera 180 degrees and restrap over your shoulder? I know that sounds silly but it often changes the lens angle to point down.
I’ve seen those Blackrapids in use and they seem pretty sweet.
I’ve also watched as a Rueters photog’s EOS-1dsmkIII did a head plant off of one at a press event because it came loose. Ouch!
Keep it tight!
I’ve wondered about that. Couple people I know use mount it to their 500s and swear by it. Insurance is nice but not a phone call Id ever want to make.