It's hard to think of anything better than either the Flats or Bowls for the MS-2(i). Most people are usually divided between the two camps (I belong to the Flats side). I have the C-pads too and absolutely dislike both the fit & sound on my MS-2. The few reports I have read here also point to the same conclusion. To put things short, the C-pads similarly change the sound as do any other Grado pads: more balanced bass and treble but with a suck-out in the mids, leading to an artificial-sounding presentation (that's my personal finding btw).
The MS2i is pretty heavy to begin with so all flats/bowls/HD414/comfies will put on some pressure to your head. I don't know much about the C-pads but they do seem to be really comfy but I would be more concern about the sound it might give, less bass, less upfront, less grado'ish, when the MS2i is already quite polite.