FlashForge Creator Pro - reversed fan duct

I tried to print one of this: http://www.thingiverse.com/thing:191297, but it requires a longer screw which I just don't have.
The longest screw sold by nearby hardware store is 35mm, which is the same length as the ones that came with the machine, and they were just too short, I need the extra 5mm...

So I just designed my own!

This duct serves as the spacer, the fan housing, and the fan duct.
I install the duct with the original 35mm screw, then install the fan, and yeah no extra 5mm needed.

You can still mount the fan to the cartridge, but this way:

1. you will need 2 very long screw per extruder, that is, 11mm for fan, 12mm for spacer, 1.5mm for heat sink, 15mm for the aluminum mounting block, plus 5mm into the stepper motor, that's 44.5mm, so you might want to get some 45mm M3 screw...
2. you lose the ability to quickly switch between PLA mode and ABS mode.

I designed a cover to change wind direction, so it's a easy switch between PLA and ABS (or any material you want it to cool down faster or slower)

1. when printing PLA (or other materials that requires faster cooling), you cover the upper air path and have the fan reversed (sucking air from the heat sink), so the wind blows around the just extruded material.
2. when printing ABS (or other materials that requires slower cooling), you cover the bottom air path, leave the upper path open, and have the fan forward (blowing air into the heat sink), so no air blowing the just extruded material.