Are they using the same mounting brackets? I checked their product page and it just says that they are all using SecuFirm2™ Mounting Kit. Is there any variation to this? The reason I'm asking this is because of this review stating that NH-D15's mounting bracket won't fit the Asus Sabertooth Z170 Mark 1. However based on this review using NH-U12S, he was able to mount it without issues on the Asus Sabertooth Z170 Mark 1. If they are using the same mounting brackets then chances are that the NH-D15 will work.
EDIT: Just noticed that the mounting brackets of both coolers are installed differently in their normal orientation. I wonder if that is the reason why U12S does not have any mounting issues.
EDIT: Just noticed that the mounting brackets of both coolers are installed differently in their normal orientation. I wonder if that is the reason why U12S does not have any mounting issues.