That cooling mod does not do much!
I did the same with my DM800 and the HDD temp was still 58 D.
I also had to "blow" into the fan to get it started, as it´s just gets 5V. from the USB.
Then I bought a HDD cooler with 2 fans, mounted it on top of DM and now it´s 38 D. And I dont have to "Blow" to get it started, and it´s very silent!
So anyone thats wants to cool down the DM800, buy a HDD fan!