After reading other threads in this forum, I realise we are on very, very different levels in terms of productions, assignments, crews, clients… I’m just a one-man-show-guy from Sweden who likes slow motion. 
Anyways, maybe this is useful to someone.
Setting:
Sweden, 28° celsius/82° Farenheit. Summer house surrounded by forest that blocks wind, buildings/walls that reflect sunlight. Basically no wind, the property is a sweatbox. We went in to the barn and wiped of sweat and drank water every 10 minutes.
My thoughts:
I thought the Spark would shut down. Honestly, the camera+lens was so hot it was ridiculous! Our bodies shut down before the camera, basically. Light blue t-shirt turned into dark blue t-shirt because of sweat. When I leaned over the camera, sweat was dripping onto the camera body and screen, very annoying. But, the Spark kept going. Absolutely ZERO issues, regardless of what setting or lens I used, and I tried so many combos today that I canoot even remember. I had it on the grass, in harsh sunlight, probably for 20 minutes at the time, while we prepared the next shot. I tried to keep in the shadow when I could. But again, ZERO issues! Good job Pixboom!
Small issues:
If it’s the heat or the high frame rate I do not know, but the touch screen on the camera works quite poorly when it’s hot, in direct sunlight. I had my camera on fan level mid. Maybe stuff works better in fan lever high.
Adding to the wishlist for Pixboom:
Make it so that the GUI has a “go slowly backwards” button that you can press and hold. When I watched all my clips today, I could only rely on the very, very small area on the screen, and scrub my finger back and forth. It was very unresponsive in the heat, and it seemed like the higher the framerate was on my clip, the slower the responsiveness was. We just wanted to watch the exact moment of the bullet hitting the can, or the axe hitting the log. This was very difficult, and required a lot of waiting time. Because, if I went back, I went back like 1 minute in playback time. The x1, x2 and x4 playback speed helps a bit. But a function to go backwards slowly would help.
If anyone wants a RAW clip from this video, let me know. I’ll set up att WeTransfer link.