HI,
I had the same idea, capturing the EOS 5DMKII HDMI Output through mi IO HD, but the first try was not successfull. Did you get your system running?
Somewhere i read, that during live view and NOT recording the hdmi output was full HD, so I guess somehow it mst be possible to capture that signal.
There might be another problem: The IO HD supports only 1080i30, but the EOS delivers 1080/30. Maybe the IO HD does not understand that incoming format.
Maybe it becomes neccessary to buy a AJA min Converter HDMI to SDI?
Hopefully you have a solution.
Thanks
Tim
p.s.
I am wondering, why there is only you and me who had this idea, or did you find anyone else in the world wide web, who has this problem?