Except nothing is being cached for that particular subdomain. I have a rule that sets the cache level to bypass. My origin server has a symmetrical 500mbit/s connection, so even if the file were not to be cached by CF because it exceeds the max. filesize of 512MB, wouldn’t it still download fast? Have been a CF user for over 5 years now, and have never seen this behavior with big files.
Also created a bypass rule just for https://f.koningnet.nl/1GB.bin, which is currently active.