Modding the Takstar Pro 80

I have long wondered how I might treat the inner surfaces of a phone with something a wee bit softer than the hard smooth plastic. I have seen some attempts where people have glued different materials to the inner surfaces, but getting around to treating all surfaces is not doable in practice, so instead I looked to another solution: "Stone Chip" protection spray. This is a rubbery mass that is sprayed onto cars to protect the lacquer from stone chips that will lay the metal underneath bare and allow it to rust. It is a rubbery substance with an uneven surface once dry. I thought to myself that this might be a good solution for headphones. It will add to the mass of the phones and hopefully reduce resonance (as if I have ever thought to myself I heard any phone resonating, NOT). The rough surface will hopefully diffuse reflecting soundwaves.
Anyways, I covered all that was not intended to be sprayed with masking tape and got ready for the big "SPRAY-'N-PRAY"
Actually, I also removed the white plastic in the middle of the cup beforehand.

This is the two cups after I treated them with "Stone Chip" spray.

This is where I decided to try something else than what I originally planned. Leaving the centre hole would increase the inner volume of the cup and since I could not be certain of a perfect fit for the metal shell to the plastic ring I was worried that the phones might leak sound and that is a definite no-go in the office! Luckily I had a bunch of IKEA Cork coasters lying about so I used the plastic ring as a template to cut a piece for the metal shell.
"Why Cork?" you might ask. Well I had those coasters lying about, and also, cork is widely known to have good sound insulating properties.

Oh, and it actually fit inside the metal shells!
That is it, I did nothing more the the phones themselves and instead went on to make a better cable!