Yeah I have seen this cooler, and it looked like a really nice candidate for N-ATX, but I haven't thought about using it with slim fan under the finstack. Which is weird since that's one of the first things I tend to look after.I just realized that the Phanteks PH-TC12LS has what looks like cutouts underneath the finstack for a wire-style fan mount. I've sent an email to Josh from NFC Systems in hopes that if he owns the cooler, he can test to see if an Lp fan would collide with the mounting hardware. If not, I can mount an underslung fan and get the x99 cooler clearances that I need for this build.
So I agree with you, it looks like there is enough space for the fan, and it shouldn't collide with the RAM. But yeah, mounting hardware is another story and should be verified, but that can always be modded
just found this gem:
Today I will be reviewing the Phanteks PH-TC12LS CPU Cooler. CPU coolers can come in many shapes and sizes. Some cases have the room for monster sized coolers. While other, compact HTPC, cases of course have very limited space for cooling. Phanteks has risen to the occasion with the PH-TC12LS...
And this nice picture:As you can see in the pictures the fan takes up most of the clearance dimensions, so if you mounted a slim fan this cooler could fit into some really tight areas. One thing that may arise is the clearance between the cooler and the Northbridge heatsink. Some motherboards have taller Northbridge heatsinks and that could be a serious issue. Clearances around all the other components were more than plenty and I do not perceive any issues with ram as there was enough room to accommodate for ram that has a big heatsink.