I have zero personal experience with lowering springs on 5th gen Camaros, however, I would choose springs from a reputable suspension company. Some examples are Pfadt, BMR, Hotchkis, etc. I'd trust a specialized suspension company more than Summit.
I have nothing against Summit parts. I've used their parts on cars before and they were fine. I just think suspension parts are important enough to not use a "discount" brand though.
2011 Summit White Camaro 1SS/RS
-6.2 LS3, TR6060, 3.45, G80
2004 Black Silverado 1500 2WD Regular Cab, Short Bed
-5.3 LM7, 4L60E, 3.42, G80