Update on the MK801 pad swap:
I received the Beats Studio 2.0 pads, and they do
not work on the MK801. However, after studying the problem a little more (and numerous other pads), it dawned on me that I failed to try even the simplest and most logical solution! The stock pads are so small that the HM5 pads (including Senitek) fit right OVER the stock pads. It's easy to pad roll to your heart's content, and it is completely reversible.
The comfort is night and day better!
I pad rolled with each of the pad styles (pleather, Senitek fabric, and velour). They each tweaked the sound in their own unique way (ie pros and cons).
In end I settled on the hybrid version:
Also, for even more of a sound improvement, I also found a tuning mod. Sinply remove the stock pads, remove the 4 screws holding the cups together. Then behind the driver you will see a thick piece of dense foam. Remove the foam, then put everything back together (including reattaching the stock pads, that have a clip at 12, 3, 6, and 9 o'clock). THEN add the HM5 pads over the stock pads. The foam is too dense and thick IMO, and chokes the stock driver. I much prefer the sound with the foam removed.