My first mod for Meze 99: pads-rolling to Fischer Audio FA-003's pleather pads (I happen to have some of them around).
They are loose-fit for the Meze 99 (as the cups are smaller). But thanks to the smaller pad-hook-opening (whatever they call, it's where you insert the pads into your cups), they do stay nicely. This improves the comfort of the headphone quite noticeably, while taking away none of the sound quality/signature.
To quote myself in my previous short impression:
Now all those problems are gone. The FA003 pads have enough depth and are big enough to fully cover my ears. I can wear the Meze 99 for hours without feeling any ear-pain now. And it's even better than FA003 itself, since Meze 99 has ways ways better fitting mechanism and clamping force.
Since FA003 is more-or-less the same headphone as Brainwavz HM5, the HM5 pads should fit the same way.
Off topic: I really do think that if designers/manufactures don't know better and/or don't have better pads .... compatibility with FA003/HM5 pads should be a must for headphones. They are relatively cheap, readily available, and very comfortable.