Actually, WB recommends a seperate RL for the Superfly. I have used both, I like the CRL for its ease, but I found that by using a sererate RL and Dutch Stingerz that my tarp pitches tighter more consistantly. And I also found that there really wasn't much fussing to center the tarp either.
Both methods work, and work well. I personally found that the CRL was easier if the distance between the trees stayed consistant from hang to hang, but if the distance changed much, the Stingerz were the way to go. YMMV.
All, I can say is try one and if you like it, stick with it, if you don't or feel the need to tinker (and I do
) then try the other.