I decided to just go ahead with the stuffing and see how it works out.
I noticed that the faux-leather exterior now clings on much more loosely onto the white ring because the carbon foam isn't as thick as the stock foam. Also, when I wear the cans now, I can feel some excess faux-leather material bunching on the sides of the pads. Is that to be expected?
I actually find that these modded pads fit a little better since they aren't bulging out as much as the stock pads. I have large-ish ears, so the tip of my left ear now touches the damper, but it doesn't bother me. I'll report back to see if this changes after an extended listening session.
As far as the sonic effects of the earpad mod go, I definitely noticed that the mids are now more forward and in-your-face. In fact, the upper mids and lower treble seem to be a lot more forward too. No more recessed mids now, these sound more natural and balanced now, and vocals are definitely more engaging and easier to follow. Also, I am noticing slightly increased treble clarity and sparkle, probably because of the removal of the mesh cloth. I don't think the bass has changed very much--it just seems less overemphasized because of the bringing forward of the mids.
If there's anything I'd like to tweak, it might be to have the mids be a wee bit less forward. I might just need a day or two to get used to this new sound signature though.