Find a better alignment shop. The lower ball joint plate can be shifted on the end of the arm to gain a half degree at least. Some caster adjustment can also be found that way - most shops look at 240 and claim "there ain't no caster adjustment". They don't know where to look is all.
If they claim springs will help, push down on the rear bumper on each side in turn, and see if the readout numbers change much. That's what springs will do.