OK, This thread just cost me!!!
I have the RS-7 and have been very happy with it, but I find many times I want two cameras with me - my 7D and 6D. I have also found my Carabiners do come lose at times. So I just ordered the Yeti Slim Dual Harness with Locking Carabiners.
I could really use it this weekend as I plan to be in an area with great landscapes and great wildlife so the 7D/100-400 and 6D/24-105 combination would work really well. Problem is the harness won't arrive until middle of next week.