Hi Tim,
That was very well written. As a new climber, I completely agree with redundancy but have not found a easy way to have a backup to my friction hitch other than my lanyard. What do you use?
I have considered getting this
http://www.treestuff.com/store/catalog.asp?category_id=280&item=1499
Thoughts?
Thanks, JayT
Hey, totheTREES!! Sorry I missed your post, and left your question unanswered for so long. What I use is this item up above my Rope Wrench, with a biner through it, and a four foot long dyneema sling going to biners on my side "D's".
http://www.amazon.com/gp/aw/d/B0045...i+ascender&dpPl=1&dpID=510cnPWplTL&ref=plSrch
It is a cammed ascender, so I do not have teeth on the rope above my hitch. It runs up the rope with just about zero resistance. I just hook my left thumb through the steel cable loop and raise my hand up the rope. I connect my knee ascender's bungee cord to its biner, so every time I raise my left foot, my knee ascender rises. My bungee cord is thin enough and weak enough that it doesn't impede my attempts to raise the Cmi ascender, but strong enough to pull the knee ascender up the rope. The Cmi ascender is a one-way device, however, and does need to be unweighted in order to release.
I tend to leave it on my rope until I've gone as high as I want to go in the tree, and then need to have the ability to either drop down lower, or to move laterally up and out on a limbwalk using my 2nd rope and climbing system. At that point my Cmi ascender gets converted to duty as a 3 to 1 mechanical advantage system, with the addition of a small pulley, for the limbwalk.
The device you showed is one I had not seen or at least noticed before, so thanks for posting that link. It looks like a really cool device, one that I would like to own and play with. Without having used it myself yet, I can't say whether or not it would be appropriate for the task or not. I do not know how it does what it does. I suspect strong spring pressure holds it in place on the rope, and that it is somehow designed to be able to easily slide in either direction if pulled along at relatively slow speed. I think a higher speed jerk on the device will probably cause it to grab hard, just the way a modern seatbelt in a car operates. You can adjust your position slowly, but in the event of a high speed crash the seatbelt almost instantaneously siezes up and prevents you from slamming into the steering wheel and dashboard.
I guess my concern would be about whether or not the device could inadvertantly drop down onto your hitch or your Rope Wrench, causing a failure of the system. Like I said, I haven't used one yet, but I'd like to. As always, I'd want to use it low and slow first until I felt certain it was bulletproof.
The use of a knee ascender below your hitch also provides an extra layer of safety or redundancy in your system, which can catch and hold you if for some reason your hitch fails to hold. Plus a foot ascender below that.
Thanks for your post, and for showing me a device of which I was unaware.
Tim
Here's me: "Hey Chris... Hang on a sec... I gotta throw the porty on real quick." 
Thanks for bumping it Lawrence.
