I just read Tandem Flies. Charlie Meck suggests attaching dropper flies by using a loop-to-loop connection. (The fly is looped directly on to, and close to, the leader.) However, when I tried to take the flies off, the loops seem to lock. Is there anyway to prevent this from happening? I'm even thinking of adding petroleum jelly on the loops.

I also had this problem several years ago when I put loops on flies to pre-rig them, and then attach them to a loop at the very end of the leader.