2" is all I needed as well. Keep in mind the hum is only noticeable on high gain and iems. Not really something you'd even really do but once you know it's there... you do what you can to remove it. I use mine in a desktop rig under my screen so it made more sense to put the supply on a platform on the ground that raise the amp and screen to match
Out of curiosity, I decided to try my UM Miracle CIEM's with my GS-Xmk2 to see at what volume a humming would start.
With the GS-X's volume knob being used as a clock and on low gain, also the CD in my SACD player on pause, a faint humming started just after 3 o'clock pm, but because my comfortable listening volume is 8 o'clock am, I think my ears would start bleeding if I was to put the volume at 3 o'clock, but not only that, I would probably end up going deaf.