try before you buy!,A arb sales man tryed to convinced me when i was looking for friction hitch cord for V Ts ,what i really wanted was a lock jack....so i brought one ,not from him as he was too expensive but none the less i climbed on it 3 times and get the feeling ill never have the control of a friction hitch so its stays in the bag untill i get more time to practice on it...descents are bloody fast so two hands are needed,cant realy kick off and swing for a limb whilst using one hand to control the decent and the other to grab the branch your aiming for,unless i have not mastered it and theres somthing i dont know that is my biggest turn off for the lock jack,also i think coming down well to fast and letting it off the second time i used it,the jolt realy hurting my back for a few days that was probably my second reason for not liking it......... ascending is fine though,very smooth!
I would like to know what the spider jacks like though but untill i find a mechanical ascender i like then ill be sticking with friction hitches