I have HUE+ in my Skylake build (full specs in my sig) and while HUE+ controller has same length and width as 2.5" SSD drive, it's thickness is twice of the regular 2.5" SSD drive. By thickness, it's as thick as 3.5" HDD drive.
Even though you can't mount it into the SSD drive slot, you can mount it just fine into the HDD drive slot, provided you don't have HDDs there occupying the space. Your case has 2x 3.5" HDD drive slots.
case specs: http://www.fractal-design.com/home/product/cases/define-series/define-nano-s-window