i think Gord is on the right track with the sleeve deal, that many friction hitches have this. Looking at VT, Distel, Schwab, Knut; it seems that 4 uninterupted coils gripping a host line, with a previous bend/choke in the host line is fairly secure! The bend can give some of the grip, taking that load off coils; allowing them to free up easier(?). A VT places a gauntlet of several bends in the line; i think these bends give friction, but slide controllably too as they aren't choking the host line; so gives this buffering of the load with non gripping friction; leaving final friction to the positiveness of the coils. The more reduced load after running thru the trail of counter-bends under VT give it it's prowess i think.
The double braids Brian recomends etc.; seem to have enough stiffness to pull open the coils on unloading, getting a stiffness to do that yet grip posititvely can be a trick logically i think! But, matching this semi-stiff line, to a larger host line; allows us to keep the stiffness property to help in release and maintain shape, yet the property of the chord being smaller diameter assures the proper grip, allowing both properties IMLHO.
Orrrrrrr something like that!
:alien: