I had a version of this system that I could switch from long to short without ever being "unclipped.
I tied my friction hitch, then connected it to a pear biner, along with my spliced end of my climbing line. Let's call this the hitch-biner. On the bottom of that hitch-biner is a 30" sling with a carabiner at the end of it. I clipped that to the bridge on my Master II saddle. The whole setup is now floating 30" from the bridge on my harness.
There is ANOTHER 'biner floating on the bridge. We'll call that the bridge-biner. When I want the sytem short, I bring the hitch-biner down and open the bridge-biner, so now the hitch is floating just a 'biner's length from me. When I want the system long, I open the bridge biner again and let the bridge extend up to the end of the 30" sling.
I'm always secured and I can extend and shorten the system while hanging in mid air.
Does this one need a picture?
love
nick