Who is CC&G? You mean GG&G of Arizonia?? As long as the mount places the ACOG at the correct height, you should be good to go. Mounts like the GG&G, LaRue and ARMS give you quick-detatch capability. I have the ARMS mount for my ACOG. Although I much prefer the LaRue, the ARMS has been good enough for me. I don't plan on swapping it anytime soon.
I had my EOTech mounted directly on the receiver. In this position it co-witnessed the irons with the center dot of the EOTech on the tip of the front sight post. Mounts like the LaRue offer the QD feature and raise the optic to where it will co-witness your irons in the sense that you can still see your irons through the optic, but now the EOTech dot will be higher than your irons. The irons now exist in the bottom third (instead of dead center) of the optic window. Many people prefer this because the irons don't block as much field of view.
It doesn't matter as much to me if I'm using a flip-up rear sight. If that is the case I don't feel like my front sight is in the way too much.