Don't even bother with the second fan. A push/pull set up on that heat sink is pointless. Usually the space between the second rear facing fan and the rear chassis exhaust fan is so small(especially on a mid-tower)that all you end up doing is disrupting the flow of air through your case. When that happens your chassis temps go up and ultimately affects your other components. If you're getting high CPU temps with the 212 using one fan then go liquid or get a better heat sink. Just remember this rule of thumb fo air flow, intake from front/side/bottom, exhaust from rear and top. stick to that and your CPU temps will fall. The 212 is a great product and performs really well in ideal case conditions.
I´ve found better results from fans actually pulling air rather than pushing it through the HFS but it depends from the design of the HFS. Try moving the fan to the back of the +212 and have it pull the air and see if it works for you