No chance for updates yet, but . . .

. . . here are some pics of your theoretical cable . . . IIsiColorPivotII_PDS_Card_HackProject™

I didn't feel up to deciphering the pins that are tied together until you chimed in with some silly-scope data, my working hypothesis was sense line voodoo and I'm a bit rusty on the subject.

Anectdotal data on the Vertical Sync rate is above. Lines of research to be attempted: UNDERClocking a Video Card??????