Hi,
Check out my first video with the action 2.
I had it set for 4K 30fps and I recorded outside and had no heat issue at all, with the caveot that it was 48 degrees and pretty windy.
The first thing that impressed me was how good the internal mics handled the wind noise.
I also used the magnetic neck mount under my shirt.
It's probably still processing the HD and 4K.   It was just a quick video and I didn't move the kayak around so the sun was at the best angles.
I was pretty impressed how it rendered the sky with the sun directly in the sensor.

Please check it out and leave a like for me.  
thanks :-)

Amazing footage, snorkel! Thanks for sharing this with us.

Nicely done.    

Very nicely done snorkel.    Action 2 performed quite well.

Looks very good!

Nice video Snorkel!!