I never saw that e-mail. my experience is the CPU/system temp is fine. System temp doesn't go above 70. Fan does increase on its own. without the miner running. Airflow is the key to cooling and those bottom vents and spacing in original design don't give enough airflow trapping heat causing fan to run faster. All dust falling to the tabletop get sucked into those vents. To lay flat there needs to be at least 1" of space below apollo to allow for proper airflow volume as fan speed increases. The top vents would have to be double the width. Fan speed and sound is always my key indicator to how efficient a system is running. Faster fans means higher temps needing more airflow. In this case constricted airflow needs higher fan speeds.
When my miner is running system temp is 43C with cpu idle and miner at 68-70C. 3600RPM. This higher fan speed seems to cool the cpu fine. Laying the apollo flat in eco mode works fine and the fan speed is quiet enough.
RE running miner outside. Other than ambient humidity and environment. I think the Miner should run fine in turbo mode and keep the miners cool. Fan speed is key. You need faster fan speeds to move the air to cool the miners. For longevity of the miner processor i think those temps should stay below 75C. With antminers those fans would keep the miner temp between 60 and 70C. I ran antminers outside in the garage and they ran great with temps below 60F. Lower fan speeds keeping system cool. Running these fans at full speed helps move maximum airflow but does put stress on those fans causing higher risk of failure. Running at 3600RPM/half speed and the fans can last a long time with very low risk of failure. Always listen to the sounds your fans are making.
Case Study: I just turned my apollo down, lay flat running in balanced mode. Temp increase to 72-74C on the miner. Fan increase 4000 to 4500RPM. No change in system temp 43C. So that email suggestion is a big fail on my apollo II. Dust is building up on top slots after 2 months of running so will need to be blown clean soon. Bottom slots on the side operation seem to be clean and cool. Isn't the bottom where the raspberry pi CPU is located?
I agree mine acts the same way as yours. Even the case runs cooler sideways with the heatsink pointed up.
I copied the part of the email they sent out about placing it sideways ( my first thought was your post):
Running your Apollo II in Balanced or Turbo mode requires more airflow over the top slots to keep the power supply cooled with our passive airflow technology.
The Apollo II is designed to be run on a flat surface that restricts the amount of airflow that goes in through the bottom vs top this means:
1) DO NOT place your unit sideways. While this might reduce fan RPMs slightly it will cause your power supply to over heat due to not enough airflow through the top. This is also the case for shelves that have wire mesh or not a flat solid surface