Fans are usually mounted as pushers, and we all know that this works.
I built a series of machines for our company and the tall ripjaws ram interfered with the fan. I mounted the fan about 1/4" higher to clear the ram, and it worked fine.
On the second machine I put the fan on the back of the heatsink as a puller. It worked fine too, and provided lower temps than the pusher fan mounted a little higher.
I was using Xigmatek coolers and fans. They are easy enough to mount but once the fan is mounted it is more trouble to unmount it and move it so I didn't experiment with it too much. Maybe it is easier to move the fan around with the 212 and you could try it both ways to see which way cooled the best.