I find these foams perfect: http://www.ebay.de/itm/2-Ersatz-Ohrpolster-53-mm-zB-passend-an-Koss-Porta-Sporta-Pro-Kopfhorer-/130866048343?hash=item1e78396d57:m:mM5HSm8COZLAeA9XbS0ohJA (They're bigger and softer and work nice if you want to use a headband)
And these headbands worked perfect for me: http://www.amazon.de/HCH-ECO-10-Stück-Einwegkopfhörer/dp/B00XL318HW?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00
This is how the finished headphone looks: http://imgur.com/CKvYtVQ
I really love them and they sound so much better than my $250 Sennheisers which were also very uncomfortable.
Greetings all! I know this is an old thread, but if anyone stumbles across it I thought they might find this interesting. Recently I decided to give the KSC75 a shot and was thinking of doing the Kramer mod when I decided that instead of drilling holes in the stock grill, I would 3D print my own grills to replace the stock ones. I can gladly answer any questions about them. I think they sound pretty good (especially version 4...V3, not so much though).
stock vs v1-3:
That is really nice. Is it possible for you to post the 3D print "files" (not sure what it's called) so that I can reprint them?