Give this a try if you are hankering after Emerson's GX1 as featured in the song "Pirates", or "The Score".
"Growl" is mapped to aftertouch. I remember trying to map it to mod wheel but I never got it to work.
Also, for some reason this patch can distort at high volumes, especially in the stand-alone 2.6 version. This is a bother, because the same patch did not have this problem in 1.6.
Enjoy, and if you improve it, please let me know with a reply.