This is the customized version of http://www.thingiverse.com/thing:204007

This is for 80mm fan, it fits perfectly.

The holes for the srews are 3mm.

Using the following options:

mount_screw = 1.7
extension_screw = 1.7
mount_angle = 90
fan_screw = 1.7
fan_size = 80
extension = 1
screw_spacing = 72
extension_length = 20
mount_position = 35
extension_mount_angle = 90
mount_length = 12
full_plate = 0