Quiet Raspberry Pi 4B case with active cooling

I wanted a very quiet Raspberry Pi 4B case for playing around with it as a desktop, but knew it needed active cooling.
I ordered some 28mm x 28mm x 20m heatsinks and designed this around them.

Design considerations:
* Use a large heatsink so minimal airflow is required. I provide an easy to print alignment tool to ensure the heatsink is properly positioned for the cover to fit.
* Duct the airflow through the heatsink, don't leave proper airflow to chance.
* Duct air in one side and out the opposite to maximize the likelihood of pulling fresh air.
* Squirrel-cage blowers can be much quieter than fans and handle pressure differentials (from restrictions) far better, so I used a 4010 blower.
* The primary source of noise for a blower is the intake, so I wanted the intake fully inside the case, that meant it's going to be used as an extractor.
* The second loudest source of noise from one of these blowers is the backside, where the motor is mounted. Fully enclosing the blower ins