I talked to a MacDon representative last summer about putting a 30 ft FD70 on our 9510. He said that he wouldn't recommend putting the FD70s on anything older than 50 serious because of the HHS.
I would think you could do the same update as would be required to put a 600 series hydraflex on the 9600 though.
However, my disclaimer is I have no personal experience on this, just what that representative at a farm show said.