I don't know that I would use poly in the rear links - you need to have some flex in those bushes.
Poly is fine when the movement is in a single plane (like the front control arm bushes), the rear links on the other hand, move in a single plane only if both wheels move together - if one wheel moves more than the other (as is normal) the rear link bushes will rotate around the center bolt and also twist. Poly, because of it's nature, will resist this twist and limit flex.