I know this thread is old, but it's the first result from Google when searching for this. I am building a system with these components and would like to clear the air:
An upper side-panel 25mm fan does NOT fit with the Hyper 212 Plus.
I didn't think it was going to, and when I attempted to put the side panel on, I found out for sure. A 20mm fan MIGHT fit, if there even is such a thing. I think I'll mount the fan on the outside of the side-panel, though I need longer screws for that. The lower side-panel fan does fit fine.
Other issues with this build:
Corsair Vengeance RAM with the tall heat-spreader BARELY fits in the slot nearest the Hyper212+. It's basically touching the shroud of the fan. However, I'm not using that slot anyway, so idc.
There is an opening on the motherboard tray to access the rear of the socket to give you access when installing a cooler. However, the 2 holes on the left (when looking at the back of the mobo) are not fully exposed. I was BARELY able to hold the nut on there while screwing the bolt in, and I had to hold the nut with wrench.
The front fan doesn't really blow on the top-most hard drive in the 5-slot HD bay. Probably not a big deal, but it would be nice if it was a 200mm fan instead of 140mm.
The right side-panel (not the windowed one) is a tight squeeze due to sata power & data cables that stick out the back of the hard drives. I am using 90° data cables but my PSU didn't come with 90° power cables. It fits, but barely. Would love it if this case was about 1cm wider.
Be sure to route the 8-pin ATX power cable before screwing the mobo down. I didn't, but was able to just unscrew one screw and feed the cable through the upper-left corner.
The plastic things that are supposed to hold the video card in are worthless. They don't even come close to closing, so I removed them and was able to screw in the video card. The holes are actually threaded, so that's good. I don't think they expect you to use those with a video card honestly.
Otherwise, this build is pretty sweet. I hope this info helps someone else out there.