That fact you say the pistons are damaged can't be helping! lol.
Also if your using tapered pistons, they feel a lot lighter and bouncy compared to standard pistons.
Ive just got standard Durango pistons which ive glued up and drilled out myself. My car doesnt feel bouncy at all, even when pushing the suspension up and down whilst the car is on the bench.
Im on 3 hole pistons 1.7mm rears, 27.5wt oil, light blue springs. For the front im on 2 hole 1.8mm, 45wt, dark blue springs.
The front actually feels quite stiff, so im really not sure whats going on with yours
.
Can only put it down to using non standard durango pistons, which are tapered and possibly damaged.
Craig