Customized version of https://www.thingiverse.com/thing:21112

Created with Customizer! https://www.thingiverse.com/apps/customizer/run?thing_id=21112

Using the following options:

holeaccess = Flange
$fn = 80
smallsize = 40
largesize = 60
smallflange = 3
largeflange = 3
wallthickness = 2
cowlingheight = 10
smallholes = 32
largeholes = 50
smallholesize = 3.5
largeholesize = 4