Were you ever able to figure this out?
I have an HDMI cable connected from the STB to the Slingbox HDMI In. I have another HDMI cable going from the Slingbox HDMI Out to the TV.
The picture on the TV goes in and out when connecting through the STB and the same happens on the Slingbox app (but not at the same time).
I can't figure out how to make this work with these new boxes.
Any advice would be much appreciated.