Oh the foam insert ring was removed by default. Like I explained in the first post, I found the foam insert ring to be bad for the earpads both in terms of comfort and sound.
Not much give with the pleather casing I'm afraid, it's a fairly tight fit with the original memory foam inside.
If you really want to increase pad depth, I'd recommend that you use something that goes between the earpads and the mounting ring, rather than cramming more stuff into the earpads themselves. As to what exactly could be used in between there without compromising the sound, I don't know.