Right so after hearing the sad news (of it snapping) + some recommendations from another head-fier:
I decided to keep them (and not send them in for a refund)
-> I had bought the item from a UK seller which posted to the UK, and as I went home for several days, I picked up my snap-ons, however wasn't able to test it, let alone stretch it for my D2K's.
So I decided to "bite the bullet" and take it home (to france)
I have to admit its not as straight forward or a pleasant experience.
I had to stretch the snap-on width wise...and to be quite honest, this thing is well built...for its original purpose, not for the denon's.
Anyway, so as I started stretching it, I could hear the material tearing. So I stopped, then continued on the other side (hehe)
I ended up "giving up" - I went ahead and did the logical "mathematical" approach.
Why "bolt" them all on, when I could just do the outer edges?
Ok it won't look as pretty but there are two advantages from doing this:
1. It won't damage the leather at the top of the D2K's
2. It will fit, and not actually rip - meaning a wasted £16.
So here it is, beyer snap-ons -> not so perfectly on, nor good looking, but certainly more comfortable on my head with that extra padding.
I can finally wear these without having "2 metal wires at the top of my head"
I also realised that due to the added padding, i've had to add 1-2click of size on them denon's -> which is GREAT for me :)
(click for higher-res + size)
Top view:

Side view:

Front-end view:

Rip - within the beyer pads (centre in this case, also happened on the sides)

When the beyers are forced to be "closer together" to snap-on so to speak, it wrinkles the denon's leather (not nice if you don't plan to make the snap-ons permanent):

No pressure to close, we can see the denon's leather, just how its supposed to be.

Edited by Totally Dubbed - 3/11/12 at 6:19pm