We use the portapower at a length of 3ft approximately and use the large footpad on one end placed in the wheel well and the other end against the lower control arm. We push it slightly forward and then just unscrew the joint.
I would place the new joints both to the same depth of thread and not worry about previous demensions. The car should be aligned afterwards anyway. I would run them within 2-5 turns of all the way threaded.
Bosch Master, ASE Master, L1
33 years MB technician