(german is my main language, used google translator help)
@rubicoin
Very good made ! Removing grill is good choice.
I think about to drill all holes above cooler up to 5mm. Described it here -->
#491.
Or remove grill completly, as you did.
It is not much more dust, cause the fan rotate much lower

Overall, you safe wattage and noise.
Asrock or AMD coolers rotate with ~2000 rpm at office usage, +2,5 Watt !?
my
Noctua NF-F12 PWM, 120mm ~480rpm, only 0,6 Watt maximum.
Dust is no problem, my first A300 was running ~5 months, opened it last week to test new RAM for my second A300.
There was very little dust inside, most of it stuck on
my copper.
Bought
another Noctuas very cheap, second hand, for my second A300 and 1 reserve

Meanwhile, the fan is only weighted with the weight of the 4 long screws so that it does not fly away.
I'll screw it to the housing or tie it with a cord.
For me it's not about making the device as small as possible.
I want it to be very quiet and energy efficient.
For
USB-2.0 expansion used Audio hole.
This makes it much easier to open the device. For later cleaning
