Those are probably the 56" springs (SS length), plus the way they are designed along with the front hangar flip is causing your problems. Like jos57100 said, that eye roll although probably not any "weaker," lowers the car another inch. This is intended, for this application. Stock length springs (55") will cure the rear shackle issue. But if you want it that low you should probably consider some Caltracs to keep the axle under control. I ran my Duster with flipped front hangars for a couple years and liked the way it handled with the rear down low. Recently I put it back to stock just because it was bottoming too much.