Just my 2 cents: I've installed quite a few servers and racks of hardware in very unsuitable spaces. LTO drives in dusty rooms, important disks in hot and cold (summer and winter), dusty and vibrating rooms and so on. I was very worried about them dying way sooner than people would expect. The only thing that died after two years was the LTO drives. Everything else is still running. So I wouldn't worry much about your hot attic. 43° Celsius outside means constantly over 50° inside the server, which sounds horrible but in the last 15 years of my experience nothing died because the room was too hot, or cold, or humid, or shaky. I've installed dust Filters in front of all air intakes, though. My reasoning is, that dust kills way faster than temperature.