I thought you might like this quote from a Meridian Customer Support e-mail:

Quote
You should avoid using the audio over HDMI from the G98 as the jitter that is introduced makes this connection uneconomical in performance terms. In any case, the G98 is only able to pass two channel audio over HDMI.
I'm using 3 x SPDIF direct to the G68 anyway but it's a bit disappointing.

Malcolm