I found my Edge HD was impossible to cool down in the summer. The outside temperature drops so fast that the OTA just cannot follow. The TEMPest fans cost a lot so I decided to make one by myself. I measured the size of the OTA vent cover, and 3D printed a fan adapter that replaces the vent cover.
I removed the vent cover and screwed in the fan adapter. It matches well. I then installed a 40mm fan to the fan adapter. It looks nice and feels solid. The 40mm fan can take up to 12v power supply. I believe it cools the OTA much faster than the small fan in the TEMPest system.