As mentioned in the previous posting, it's time to have a look at Robot Damashii [Side MS] Gouf Custom's interesting Hard Point System. ^^
Since the feature is about versatile attachment of various weapons, weapon parts, and other component using a couple peg types, I think it would be useful in the understanding of the Hard Point System by locating all the connection points on Gouf Custom first. ^^
[Shoulder armor]: one round port + one round peg (either side).