I thought pumps had to run at 100% ..or Is it just aio's. Did you get a big hunk of rubber with your case?
I did... not completely sure what it's for though. (extra support for the PSU maybe?)
edit: Yeah... I checked the online manual, and it's apparently for mounting a PSU in the upper position.
As far as the pumps go... the D5's have always had an adjustable option, even the fixed "b" models ran at a set percentage of full speed. My Corsair H100 AIO had two speed options.