I have both models of the Primo's Trigger Sticks II Tripod for sitting, kneeling, as well as standing shooting and love them.
I did nearly all of my shooting in Africa off of the taller version and it was absolutely invaluable.
I flat blew two shots I should have made on the one time we left the truck without it and I had to rely in the PH's home made sticks made of something resembling bamboo.
They were terribly weak and wobbly and would not bite on rock so there was just no way to really get a sure and steady rest out of them.
Conversely I never missed a shot shooting off of the Primo's sticks.
I haven't done so yet but I've looked at trying to find a way to put a ball head on them to use with "the hog saddle" or a similar clamping device to really steady thinks up to make those shots beyond 300yds infinitely more doable.
As is though they are great for what they are intended for.