where would you place a sperical bearing in the rear trailing arms....in front( on the body shell) or at the rear axle?..i am thinking at the body shell location, as this would alow the most movement( twist)
As shown in the CRH, we put unibals in both ends. If you want the precision of unibals, do it all the way. But you are right that the major twist is at the body end - after all, the axle end is always parallel to the ground across the axle.
As you know, this twist is the reason that polyurethane bushings are not favored for the trailing arms. And for those that have tried them, the failures have all been at the body end. It might be interesting to try unibals at the body and poly at the axle.....
One (tiny) reason to use the axle end is that the rubber at the body end will absorb more of the suspension noise.
Don't bother with the trailing arms on anything but a competition car. However, replacing the trunnion bushing (cones) with a spherical bearing does wonders. Caveat: you have to upgrade the outer trunnion bushes as well for this to work. And there will be increased NVH.