Matt Laur , May 01, 2012; 06:04 p.m.
The TC17E is going to treat the 70-200/2.8 II pretty well. Just remember that it's going to reduce that f/2.8 aperture's speed in exchange for bringing you out to 340mm.
The lens mount, with or without the TC, is quite sturdy. But I'm wondering about your concern, since you mention hiking. Are you thinking of hanging the camera from your neck, with the lens/TC mounted? Don't do that - if for no other reason than because it's just awkward. There are lots of great packs, slings, bags, and other carrying rig that can let you get where you're going without the camera flopping around like that. Personally, if I were hiking hiking, I'd just remove the lens from the body, cap both of them, and stow them in a comfortable carry rig.