A proper "tuning house", like RUF for Porsche, Hartge for BMW, Brabus for Mercedes, and a bunch of others, tune the rest of the car as well, in order to compensate for the rest of the insane power increases. More often than not, they will turn in quicker times on the Nurburgring.
You all know what an entry level C-Class Mercedes chassis is. Well, Brabus makes one called the Bullit Coupé, rated at close to 800HP, 3+ seconds to 60mph, 230 mph top speed, and yes, limited production. This is insane for an entry level family coupe. For sure this little puppy, is NOSE HEAVY with a 12 cylinder and twin turbos, but I'm sure they adjusted the suspension accordingly.
Just like the Callaway, it's limited production for the privileged few, who do not want to complain, and just enjoy a limited production toy. I doubt anyone on the Mercedes forums are complaining at Brabus.
My point and question is, did Callaway simply drop the SC in their and call it a day, and if that's what they truly did, is it because the car was balanced allowing for little more room to play with with SC? It's not uncommon for tuners to work with manufacturers you know, Alpina case in point with BMW.
Just asking', did Callaway get sloppy here, or do they really know what they are doing, working closely with GM, just like some Euro tuners do with their respective motherships?