Hah, no shit. I can't remember the details, but I thought the port was a different shape from the TG16 to the SCD-ROM? (But all the corresponding male/female connector pins match up -- does that sound right?)
Either way, if that works, that's the first TG16 + SCD-ROM2 setup I've ever seen, though in this case, might as put it with the SuperGrafx as the footprint would be about the same.