if you ever want to get rid of those marbars i will take them off your hands for a good price. also, what is a yo-yo system? is it like a RADS set up where you can quickly switch from ascending to descending?

The RADS name came out about 2 years after the rec. climbers named it the yoyo- meaning you could go up and down using the SRT system. It was introduced here in Atlanta by a climber who ended up with his climbers name as "Yoyo". His straight name was Bob which everyone quickly forgot. It is the system I use when I do treetop cat rescues. Shoot a line with a Big Shot high over the kitty, climb on it's blind side, and bag 'em. "Kats in the bag!" Now you know where that phrase comes from.

whats the typical yo yo system look like? a handled ascender and pulley along with a gri gri type device on the saddle?

I use the Basic Ascender from PETZL in the top, the tail line goes down into the Grigri that is tied to the center ring in the harness, that exiting tail goes up to a micro pulley that hangs from the bottom hole in the Basic Ascender and them down again all the way to the ground. I assume someone has taken a closed up picture of this set up because we had this discussion about last year and it quickly caught on fire about the proper name of the system and why we should call it a RADS instead to keep nomenclature clear and consistent with he other parts of the Arborist world. Or something to that effect! Joe of the Jungle showed me this System for the first time at the Rendezvous in Nebraska in 2004

Here are the pictures of Tom Dunlaps set up and further disscusion at the TCIBoard site _link_:
http://www.tci-forums.com/viewthread.php?tid=524

Not only am I going off topic, but I'm straying to beat a ghost horse. I was reading through that _link_ you posted and there was a lot of discussion about the potential for a toothed handled ascender to tear up a rope if shock loaded during SRT. However, in a RADS system that uses either a Gri Gri or ID, wouldn't that device recieve the shock load rather than the handled ascender? Pretend that during a RADS ascent that a small branch broke sending the climber down a few feet. During any phase of the RADS climb the ID or Gri Gri should be the first and only device to be loaded. The handled ascender only serves as a backup and therefore could not destroy the rope. Any comments regarding this issue?

Also, and back on topic, if using a Gri Gri for descending, should it be backed with a prussik or is that overkill?

Finally, reading many posts over at the rock-climbing forum about the Gri Gri and Trango Cinch, everyone says to never use them as a self belay. Is there something I'm missing here, or are we using it incorrectly?

Hello Sitka
Some facts have been agreed upon by the "mayor experts" in the 3 main WEB Boards. (1)Mechanical ascenders do not destroy arborists ropes on the typical falls that arborists may experience. They have done extensive tests dropping heavy _object_s in a lab and have not reached the complete failure of the typical arborist rope either by Grigris or mechanical toothed ascenders.
(2) On Backing up a Grigri. The instructions that I got from the manufacturer did not mentioned any need to back it up. I posted a "Self Rescue Scenario" that occurred to me a few weeks back. It was agree upon that there was not need to use a back up for the GriGri and it could only cause more problems than it would solve. I learned my lesson.
I have never used a Trango Cinch so I do not care to give any opinion. Here is a post from one of the dealers.

"The Cinch is the latest in a long line of innovative belay devices introduced by Trango. We designed it with an eye for function, aesthetics and simplicity (It’s about as complicated as a door hinge.) so it offers up a bombproof belay for ropes from 9.4mm to 11mm. On smaller diameter ropes, or when holding falls that generate extremely high loads (In excess of factor 1) the Cinch acts dynamically, reducing shock loads to the belay system. In addition it will release easily and modulate fluidly while you’re rappelling or lowering off. The Cinch feeds rope easier than any other device, fits nicely in your hand and weighs 170gm." It sales from about 55 to 69 bucks depending on dealer.