PS. If your line was really capable of anything above 75356kbps downstream your noise margin would be considerably higher than 6.2....Yes, my line is capable of the full 80/20 when G.INP is on.
Meanwhile, the search for G.INP on the HH5A continues....
Consistently? Because don't forget temperature and crosstalk cause fluctuations so with your SNR being bang so close to the target it seems unlikely you would consistently get a higher sync at any time of the day.
That said, why are you using the HH5A if you think it sucks? Use a better device and think yourself lucky, I'm on an ECI cabinet so no G.INP anyway.