The 50lb preload is used to stretch the metal not control how stiff the joint appears. If you don't preload the joint during installation the metal will stretch later and leave you with a lot of slop. Preloading suspension components is the same a torquing a head bolt; steel stretches up to a point and it's that point you need to get to for a fatigue free joint.
-= Francis =-
[SIZE="1"][I][SIZE="2"]These, in the day when heaven was falling, The hour when earth's foundations fled, Followed their mercenary calling, And took their wages, and are dead.
Their shoulders held the sky suspended; They stood, and earth's foundations stay; What God abandoned, these defended, And saved the sum of things for pay.