Hi Eric, don`t have any 2" powermates only the 1-1/4" ones and they are both very nice!
I would think seriously about the 2x canon teleconverter? as you will still be able to use your MPCC with it . With the normal powermates you won`t and coma will be present in the corners of your images.
But don`t buy a cheaper converter as they just can`t cut it..
cheers Gary