For those interested, I've removed the "stock" cable on my USB keyboard and replaced it with a thinner, shorter A->mini B cable that has a home-made "Y" at the end. No adapters needed to work on a PC/hub or direct to the 770. I added a 100 ohm resistor in series with the keyboard power which will prevent potentially large amounts of current from flowing if I inadvertently leave the batteries connected when plugging into a hub or PC (and the batteries are discharged). This way it's impossible for more than 50 mA to flow if there's a dead short at the keyboard end, not that that would ever happen

See here: http://lbattraw.home.insightbb.com/