HDMI's biggest fault is the non-secure connection. I am always hesitant to suggest using HDMI cables behind the wall(or any inaccessible place) due to that fact. If you lose signal, it is a pain to find the problem(it could end up being a loose connection).
But, in this case, it may be your best solution. Like someone said previously, HDMI will either work or it will not(no gray area, or snowy area). So, if you can install everything with the plate, and it works, try to leave the cabling in a way where gravity doesn't pull the connection down and out, etc. Good luck!