Steering coupler question

On full tube stock cars theres probably no need for a sliding coupling, but on our street cars there needs to be a sliding coupling because of flex. The weakest link in this chain if you dont use a sliding coupling with a u joint will most likely be the bearings in the top and bottom of the steering column. They are not a thrust type of bearing, but a simple ball bearing type. If i ever go this route, with a u joint setup, tho i highly doubt it since i just rebuilt my stock lower joint assembly. I will use a sliding shaft with the u joint just like 72blunblu did.

He is 100% correct in stating that the sliding shaft is needed because of chassis and body flex

Newtons laws. The third one i believe. Irresistable force, and immovable object. The chassis flex tho it can be minimized is still there. This is your irresistable force, the u joint and steering box is the immovable object, it will push the shaft forward and back as everything moves from chassis flex, and will move the shaft in and out in the column without a sliding shaft.