I managed to fit a NF-9x14 fan under the motherboard in my v2 without modding the case. My issue was that the 8 pin was kinda in the way with my Asus Z270i, so i modded it a bit.
I dont see any cooling potential from doing this aside that my vrms are getting actively cooled (sorta). My nvme drives are still the same in temps with or without the fan.
Considering the noise comming from the fan, i wouldnt recommend it. Its the loudest in the whole case by a long shot.
Maybe you can get better results with a different mobo, but the noise would still be an issue.