TLG.... are you sure on this one? I've heard that this increases the forces on your protection, and on you, when you fall. Maybe it's one of those things where you can do it, but it's not always optimum.
yes, it does and it kind of defeats the purpose of buying half ropes to begin with ... but i believe you still *can* do it if for some reason you feel you really need to. maybe i'm wrong here, but i haven't really heard any super-convincing arguments to that effect.