Thanks for the link Jake, I've been wanting to make some myself. I have a couple original sets of Rapid Rail ladders that use this style of rope connection, they need replaced and this should do the trick.
For anyone else, I found the rope in Jake's link is 1/4" Samson Tenex for the LW stick UCR application.
BTW, I have the UCR's from the guy on Archery Talk. Concerning his design and my experiences, I believe if the constrictor part of the rope would be extended a little further towards the center of the rope, it may mean less two handed operation. That is the way my old Rapid Rails ropes are designed and they seem to operate just a tad handier. The constrictor portion frictions against the tree and allows the rope to be pulled through without your other hand holding it .