I wish I had an SG to send.
Are you considering buying one? Is that the reason for your interest?
I wonder why NEC went out of their way to make the US port different as well as the controller port? They really REALLY did not want anyone having anything from Japan.
I heard it was more the other way around. They didn't want the Japanese folks getting their hands on American stuff because of the censorship some games underwent when they were localized here (Splatterhouse for example). They felt it would tarnish the Japanese public's view of the PC Engine. That's why they included the region lockout code that prevents American carts from working on Japanese systems even with a converter.
I guess they took it to extreme measures with the controller and expansion ports.