Intel NUC 7th generation fan mod

I wanted to lower the fan noise of my intel NUC and had a Noctua NF-A9x14 PWM lying around. I thought obout replacing the top lid of the NUC by this one and mounting the NF-A9x14 to my lid. I hoped to be able to disable (/remove) the internal noisy fan and instead suck the air out with my custom lid. The air would in this case be sucked out through the ventilation slit from the outside.
Support was needed to print.
Unfortunately the Noctua fan I used had not enough pressure to suck the air through the tiny ventilation slits. If anyone has an idea on how to improve the design, let me know!