I assume you have a poly diff mount, as regardless of how well set the toe/camber etc is it will change constantly as the beam moves around on soggy std bushes.
If you want true stability get a 22mm rear arb and a poly diff mount, these can be had for as little as £25, ie a poly filled std one, just as good as a poly aftermarket one, and you know it fits 100% PERFECT, good one for the bufties too.
tabetha