I’m also seeing a non-negligible standby loss of approximately 25% overnight; the delta between Lloyd’s observations and my own could be a result of the System Controller firmware update which purports to improve idle power consumption, though another user there notes an approximate 1% loss per-standby-hour before the upgrade so I’m not sure.
I’ll experiment with your patch the next time I get a free weekend @wdouglass and report back if I see any improvement.