After listening to these I would love to see what Koss could do with full-size open back.
Did the Kramer Mod, didn't like it, filled the holes.
Opened the back, sound stage became slightly larger but negligible, it also ruined the original clarity.
Binned the drivers, ruined because the back is part of the driver unlike the Porta Pro with a separate driver (blue module).
As the KSC75 is relative inexpensive, it wouldn't hurt to open the back to satisfy curiosity.
I used a Sennheiser PX100 headband with Sennheisser HD414 yellow foam pads. Then modified the cables with MMCX connectors.
Light as in weight, bright as in sound, and now more comfortable, exactly what I had wanted in a pair of headphones.
The connectors is for when the upgraded cable breaks for any reason, I can simply pop another one on with ease.
Sometimes, less is more, or more is too much and ruins it.
I bought the KSC75 for its clarity, sparkle and I prefer that untouched.