[Yoda]

Where in 2-c-* is the CG of club head mentioned?

I can't find it.

The sketches in 2-C-1/2/3/4 assume a "centered (Sweet Spot) Impact". See 2-D-0.

In Sketch 2-C-1 #1, the two Impact Points are clearly shown to be on the Sweet Spot Plane. This fact is explicitly stated in 2-N-0: "In Sketch #1, the Impact Points are on the Sweet Spot Plane".

For further explanation of the Sweet Spot Plane, i.e., the assumed "Center of Gravity application", see 2-F.

Finally, always remember this:

"In the interest of brevity, regardless of how often any point is mentioned, every effort has been made not to discuss any one aspect more than once. So a complete definition can only be the sum of the comments about it." (1H)