Adjustable strut rods are necessary, especially with poly or delrin LCA bushings, and the reason has nothing to do with adding caster. I would definitely not use poly strut rod bushings, they're counterproductive. First, you have the issue of the strut rods not being the right length because of the differences between the poly bushings compared to the factory ones at both the LCA and the strut rod. Second, they add binding. The strut rod bushings acts in two different planes. You want them to be stiff under braking and acceleration to keep the LCA from flexing forward and backward, BUT, you don't want them to be stiff when the strut rod is moving up and down with the suspension travel of the LCA. The poly strut rod bushings will actually add binding into the system by resisting the LCA moving up and down with suspension travel. That is why adjustable strut rods are ideal. Not only do they keep the LCA from flexing forward and backward, but they move freely up and down.
And, you can actually make them the right length, which further reduces binding in the suspension. Stock strut rods will NOT be the right length if you're using poly or Delrin LCA bushings. My adjustable strut rods have been adjusted so there's no binding in the range of suspension travel of the LCA. When I was running factory LCA's with poly bushings I can tell you the length of the adjustable strut rods was different than factory (shorter). With the tubular LCA's I run now with Delrin bushings the length was different again to produce free travel on the LCA.
