I have 2020 HD58X (028695) with older style pads (moded with 4mm hole felt) . But my 2021 HD6XX came with the round profile pads. Ziddy76, are the older style pads style pads still available in North America, where did purchase yours if I may ask (Canadian Sennheiser has most likely the same stock as USA, and the pads were unavailable for a while).
As for Dekoni they provide measurements here, and to me they change the sound significantly not to recommend them.
I would rather go with the Chinese pads Solderdude provided link to.
Wrong Dekoni pads, they look identical/almost identical to the older Senn pads. They are sold by Dekoni on Amazon.
Picture used by Dekoni
I got older styl from Senn's store on Amazon.