I expect it's been thought of before but here is a way of attaching a dropper without an extra knot on the tippet. You tie your dropper onto a mini titanium ring (I keep a few ready tied in my vest); you slide a mini Drennan float stop onto your tippet followed by the ring followed by another float stop to trap the ring where you want it. Obviously you van move the dropper up and down as you wish. It's best to leave a tiny gap between the two stops (much smaller than in the photo!) to allow the ring to rotate freely - coarse anglers would call this a helicopter rig.
