I have a blackrapid rs4. I use it on my 7d with grip and primarily prime lenses but its never come loose. I periodically check the link is tight, it's no concern. I've even dropped the camera straight into the strap, I trust it.
Blackrapid make sheaths you can buy an extras with a steel cable if that's your concern. Also the double, which I don't personally own, can be used as 2 singles if desired.
Sun sniper do make double's. Not sure if each side can be separated though.
If using any of the above with say 70-200's with the tripod mount, I'll suggest putting the link from the strap on that instead of the camera to balance. That's all.
The only dysfunction is to use the tripod mount. You have to disconnect the strap.