Morgan and I worked out a new configuration of the bottom, L-shaped part of the Uni that will allow slack tending with as much ease as a well tuned pulley slack tender like in DdRT.
I don't know when it will be available for sale.
One setup that I've heard about but haven't used it to setup a shoulder/neck tether and attach it to the upper loop of the Uni. Then, the Uni is configured like a chest ascender and should slack tend quite easily. This simple setup should solve limb walking nicely.
Bowlegs has a good point. SRT in arborculture is still in it's infancy. Even though I've been fine tuning my understanding for almost 20 years until the Uni came about and Treebing's Fate setup, a workable SRT system wasn't available. Now, with the communication of the Internet we're able to move the discussion forward.
In Yvon Chouinard's ice climbing book he talks about some of the early vertical ice climbs done in Scotland. The climbers would wear thick, wool gloves knit from coarse wool. To form a hand grip on the ice they would place their hand in the right place and allow the mitten to freeze to the ice. Then, as they moved up they would pull the glove away and continue. Where will SRT in trees go from here?