Tom i know what your saying. this is a assumption based off my experience with only one mechanical hitch, the bone, but i think its harder to operate mech. hitches with the "two way tension" you've described. if i understand what your talking about, once you try to descend a little, it wants to let the line run right through right? i think its easier to control the line in that scenario when running through a real hitch.
ive had good luck with setting static redirects in a spot where ill have to go back up to anyway. i honestly dont mind just going back up to redirects anyway because its so easier to go back up/around using SRT, although i know and understand that some people simply are not trying to do that at all.