Just how tough can you be on these cameras?
Never heard of a lens being selected for it's 'flight dynamics'. Always a treat to see something different.
I am not comfortable carrying my camera/lens loose if it is likely to hit anything harder than my hip. For the kinds of conditions you describe, I put my camera with lens attached into a small sling bag (I use a Lowepro Slingshot), avoiding the temptation to carry more lenses/camera gear etc. I use the rest of the bag as my day pack for lunch etc. The weight is about the same, and the bag keeps the camera/lens safely out of the way and well protected when I am not taking pictures and easily accessible when I am.