snowcat's post: "I still have my 2-tuner standing on it's side rather than flat, and I haven't had a lockup since I started doing it months ago. My first Tablo used to reboot all the time, and it was replaced.
If anyone is having lockup issues, try putting it on it's side. I am curious if it helps."
I had to open mine up to remove the loose metal plate (read risk of an electrical short circuit) from what I have seen putting the unit on it side will certainly improve convection cooling of the bottom plate, thereby reducing junction temperature of the processor - which it what the goal is. You may even get a mini chimney effect on the inside via the small holes in the recesses which will improve the cooling of the other components not thermally connected to the heat sink.
Edit. I had to relocate my unit and before doing that decided to do a quick test. Using the IR thermometer I measured the temperature of the bottom and the hottest spot was running at a measured 44 deg C (box was idling). Put it on its side and the temperature dropped to 39 deg C within minutes. It probably would have gone lower but I had a scheduled recording coming up and wanted to finish the setup before that happened. If the temperature of the base plate was higher (like the 55C reported by some) the delta would have been higher. So, if you want to make maximum use of convection mount the unit to an open vertical surface with the bottom facing away from the surface and lots of free air space around it.