Hey, so everyone claims to have miraculous revelations, so I won't claim that. I'll just say that I've found something cool. A while ago, I bought some earpads from Koss, the most promising of them (see also: wasn't utter rubbish) was the MV1 earpads. I finally found a home for them on another SFI transplant. I'm pleased to report that they're performing phenomenally. They can get a little warm, but they put very little pressure directly on the ear. With the current damping, they have an extremely gradual rolloff below 70hz, but it doesn't disappear until 30hz. They still have the treble funniness that is the SFI weakness, but the midrange and below is perfect.
I compared the MV1 pads to the pads I had on them before and the headphones seemed to be a bit underdamped with the latter, but I can't detect any missing details using the MV1 pads in comparison to my speakers.
They're 3.5 inches in diameter, and are affixed via double-sided tape donuts that come with it. They would definitely work on Fostexens, but would look a bit weird, as they would leave a quarter-inch sticking out on the edges.