I have been using a 300mm f2.8 mk2 usually with a 1DX2 and 2x converter and have been carrying it okay on a Black Rapid strap with a quick release plate/clamp arrangement. I've just got a 500mm f4 mk2 and have started using the same BR arrangement, but feel this is really at the limits for it (and me) - I've nearly always got my hand round the lens or foot when not using bins etc.
I've not heard about the screw issues, one to watch I suppose, I can see the D loop wearing a bit, but in all honesty this happened with just a 100-400mm anyway after a while.
For longer walks or where I know I wont have much opportunity to use the camera I will put them in a bag 600AW or similar, but also to save my back from the uneven loading.
I've tried the whole lot on the tripod and over the shoulder, but found it rather uncomfortable on my shoulder over long distances, and always worry about all that unsupported weight bouncing up and down out of my sight!