How can I ensure both case and RAM compatibility with my NH-D15?

Using the NH-D15 and NH-D15 G2 coolers with RAM modules taller than 32 mm:

• Option 1 - Moving the front fan up by a few millimetres 
  This will increase the total cooler height!
  If you are using RAM modules with a height of e.g. 35 mm (3mm taller than 32 mm), you need to move the fan up by 3 mm, which increases the cooler height to 171 mm (168 mm + 3 mm).
• Option 2 - Installing a 120 mm fan instead of the included fan
  This makes room for up to 52 mm tall RAM modules, with a total cooler height of 168mm.
  As a 120 mm fan, we would recommend the NF-A12x25 PWM or the NF-F12 PWM.
• Option 3 - Removing the fan above the RAM modules
  This way, only the heatsink will overhang the RAM modules. The total cooler height in this setup is: 160 mm (NH-D15) / 168 mm (NH-D15 G2)
  In this setup, there is space below the heatsink for RAM modules with a height of up to: 66 mm (NH-D15) / 54 mm (NH-D15 G2)
  Using the NH-D15 or NH-D15 G2 with only one fan will, however, lead to a slightly decreased cooling performance.
  

An increase in the total cooler height matters, as it could potentially lead to compatibility issues with your case, i.e. the case might be too narrow so that the side panel can no longer be closed.