I completed installing the C4S into the S.E.X. 3.0 yesterday.
Completely successful.
However, I did have to reconfigure the mounting and installation of the board because of the larger Goldpoint stepped-attenuator AND the modified parafeed caps, also larger. All I really needed to be careful about was connecting the right length of wire to the terminals due to the reconfiguation of the board.
Here is a picture of the result: