The idea was to build it in the drawer but we soon realized that cooling would be an issue if we didn't provide the PC with some airflow and ventilation. Since the bottom is quite thick and so is the back, a few well placed holes would not cause to much noise.
The same holes have been made in the outer box providing some nice ventilation but not too much noise.
All fans were soft mounted with some rubber sealant which is surprisingly soft and resistant to vibrations. Also looks good and sealing out a bit of dust:
The idea for the airflow is an two intakes in the bottom of the drawer, one aided by the Gentle Typhoon and one without a fan, providing ventilation for the 140 mm Slipstream cooling the HDDs. The single very slow 140 mm Slipstream blows the hot air out of the case.
As you can see, the PSU is mounted facing the spot where we will mount the motherboard, although not using any screws, its very stable. We had plans on making a separate chamber for the PSU but decided not to because the heat will probably never build up to the lever where the PSU fan ramps up.