"WARNING!The Rope Runner is a work positioning tool. The Rope Runner is NOT A FALL ARREST DEVICE."
Of course that's just another guys opinion. And it does look like you need to use two hands to rappel much like a gri-gri with one hand on the device and one on the rope. But at $350 and 4 or more separate parts (you'll drop one sooner or later), I cant see using this for solo top rope.
After using the Kong Back-Up a while ago, I finally got out and used it again. Final conclusion: I do NOT like how it rotates on a carabiner, stops feeding, and can become loaded sideways.
I was TR soloing Country Club Crack. It traverses up and left for a lot of the pitch, and the Back-Up didn't like that. It kept getting rotated sideways (as shown in my last two photos higher in this thread), and would: stop feeding rope, and I would have to smack it back into the correct orientation; and it would sometimes stay in that rotated orientation and BECOME LOADED as I sat back on the rope. This last issue bugged me, as I'm sure the Back-Up isn't intended to be loaded in this manner, and could possibly lead to a failure!!
I was high on the route, and sat back on the rope to work on some moves. I was weighting the Back-Up when I heard a "POP!" and dropped a few inches. I looked down and saw the Back-Up in the correct position, so I'm assuming that it got loaded sideways, and corrected itself, making a loud noise and dropping me a couple inches. Fucking terrifying. I called it a day and went home, and am now looking into the standard Micro Traxion setup.
It could be the kong backup that jammed in the weird shape of the belay master carabiner... then it straightened out with more load. In that case it is due to the pairing of the carabiner with the kong backup... anyway! Let us know how is your new setup!!! Great review!!