I gave the hm5 pads the royal treatment last night. Here is what I did:
1. Because I thought that I might have cut too much of the ring originally, I sacrificed another pair of plastic rings and cut them to spec, only taking about 2mm off.
2. Then I about 1.5 inches from the total length of the inner foam ring taken from one of the pleathers so that it would fit underneath the hm5 pad.
3. But the foam ring still protruded too far past the inner diameter of the new pad, so I then cut about 1/8 inch from the inner edge of the foam pad.
This process "stretched" the hm5 pad a little bit and didn't look quite so small sitting on the he4 cups. The comfort...still supreme. The pads were a bit stiffer but still very comfortable. Unfortunately after several listening sessions last night, the conclusion is clear. The hm5 pad does NO favors for the he4 on sound quality. The bass is reduced substantially...mostly impact and weight. Mids are moved back a few rows and the treble extension is reduced (which I did find to be a good thing with the he4).
Sorry but these just don't work for me.