I initially had a 40mm fan on a heat sink for my motor and that did a good job but it recently died and all I had laying around was a spare 60mm fan. The motor runs a LOT cooler now. After a 6 hour print, I measured the temperature with a laser temp gun at 30C. This is great because I run my Y axis VREF a bit higher than my X.
I'll be replacing this 60mm with a Noctua fan to reduce the noise.
I used only one M3 screw (but you can use two since the mount has two holes) with a washer. The screw goes through the Fan Mount, Y Axis Mount and through the Motor Dampener. The fan won't go anywhere unless you really try :-)