Double strap on user here, I couldn't be without it at a wedding. Ok you get some funny comments, but depends if you are able to laugh them off - I always have a joke about it with people and dont worry what I look like, as long as I get the shot. As a user of almost solely prime lenses, I dont see a way around it tbh.
I am thinking of the ThinkTank lens belt and pouch system too now, I really like the idea of having more kit on me...but worried that the belt will pull my trousers down mid-wedding - now that would be slightly embarassing! haha
Ps, the only times I encounter problems/worries is when leaning forward to pick something up (think, Kitbag on floor) when kneeling down the cameras rest on the floor - so long as you descend slowly they wont bang down. The other thing is the swinging straps... but once its happened to you once you'll be aware of it forever more... basically when leaning over and forward (ooh er) to reach for something, both cameras lurch forward on their straps, and have a tendancy to smash into whatever is ahead of you! Again, as long as you make slow movements this wont be an issue, but it will scare the life out of you the first time it happens.
Also when going round corners I always put my free hand over the camera nearest the wall, just to be sure it doesnt scratch against the wall...
Tbh I am making it sound a lot more complex and hard work than it really is....all this stuff is just common sense tbh.
After shooting a 10hr wedding with 2x5Ds on my at all times I generally dont have any aches or pains
