Whether camber arm would be required depends a lot on the lowering amount for your particular application. The lower you go, the more likely the car will run out of rear camber adjustment. Eibach Pro Kit springs lowered our
G70 about 0.8" front and rear and the alignment shop had no problem getting rear camber dialed within spec'ed range. I can tell from the clocking position of the eccentric bolts that they are not near the max adjustment point.
The exact same Eibach springs dropped my Stinger a bit lowered, especially in the rear. The same alignment shop was able to set the rear camber at 2.0 deg but the eccentric bolt is maxed out. I'm installing the rear camber arms so I can get the alignment redone and the rear camber reset to closer to 1.0 deg. The toe arm isn't technically required, since that eccentric bolt is not maxed out yet, so there is still some adjustment range left on it. I'm most likely going to get them anyway, more so to replace the OEM arms with soft rubber bushing.
FWIW, I would recommend you find a shop that does lifetime alignment. I bought mine at Firestone for $170. I've already been back twice with the Stinger, and about to go back again after installing the camber arms.
