On my dual 30mm Powerhobby heatsink I ran the fans on the spacers, but they only included 4 spacers so I only used 2 screws to secure each fan (I secured them ok opposite corners) , never came loose even with some huge sends on my Kraton.
Definitely do run the spacers though, you'll just choke the fans if you don't.
You ccan see where the screws are in this pic.
Definitely do run the spacers though, you'll just choke the fans if you don't.
You ccan see where the screws are in this pic.