I have not tried and don't intend to.
I don't see how it will help except make the GoPro hotter IMHO.
None of the tests I saw were outdoors, everyone was indoors in a cool room, stationary.
Even DC Rainmaker's overheating tests of full of hot YouTube air because he was not engaging hypersmooth - being stationary. Simulating air flow with a fan is nice, but not moving the camera is pointless.
DC Rainmaker's tests were valid. Hypersmooth consumes full power even when the camera is not moving.
I have not tried a metal cage myself, but it is very reasonable to think it help. First it increases the cameras thermal mass. Secondly, it increases the surface area for convective cooling.
Full disclosure: I work for GoPro
Well, there we have it right from GoPro. Tell me Jon, will the upcoming 11 rectify the heat issue? I'll put aside some $$ for it if it does.
Thanks.
I have cooked more gopros than you can shake a stick at. I run them in static setups with no airflow, externally powered recording for hours and cages help a ton!
I have tried painting the cages white for the purpose of reflectivity of the sun and I have left them black. The white only helps a little in direct sun. It's all about the heat sink effect that the cage provides.
What I have found works the absolute best (for my use case) is to run a cage, pull the battery door off, and the battery out, run a cord to a battery and they NEVER overheat. If you can accomplish that you're golden.