That occasional squeaking in the right cup started getting on my nerves.
I've found the thread you mentioned - Sony MDR-Z1000 Squeaking Noise Problem - Head-Fi
and applied some silicone spray to these "plastic boxes", so far so good, the squeak is gone. The problem is plastic to plastic contact that makes that noise when swiveling cups. I'll see how it goes and if the problem returns, try some graphite instead.
Just wanted to say that I did something similar, and it seems to have worked very well.
Rather than using silicone spray, I used a tub of lithium grease.
From checking around online, most people don't recommend spray-on lubricants for anything, unless it's your only option. I think there are additional chemicals required to make it a spray, and it seems that the lubricants don't last nearly as long.
From reading around, Nerf enthusiasts and RC Car enthusiasts both seem to recommend lithium grease as one of the best lubricants to use on plastic parts, as it's long lasting, and should not react with it.
Apparently some silicone sprays do not react well with certain plastics.
I just used a toothpick to fill in all the gaps in the hinge, worked it in, and cleaned off the excess before reassembling the headphones.
Unfortunately, most full size headphones look similarly huge if you have a shaved head. (not that I like how the NAD headphones look)
I have a large head, and the 7520 look similar, though not as bad. Most headphones are designed so that the band sits off your head like that, but you don't notice it if you have a full head of hair.
I was actually wondering if anyone had found a good non-microphonic cable for the 7520. The stock cable is good if anything hits the coiled section, but there's 2ft of straight cord where it goes into the headphone which I've found to be problematic if it rubs against your clothing.