I can second Rider414's comments about the pipe.  I had my Zilla at Little Sahara, OK last weekend.  It was very hard to lug it to the point it had to be shifted.  It always seemed to jump back on the pipe and pull like a beast.  I didn't do much high RPM riding because the sand was crazy rough.  I am VERY happy with the pipe on my 500 Fanatic HRD engine.

I also had to make the mount mods mentioned above.  No problem, however.

Here is a video of me playing around last weekend.

http://www.youtube.com/watch?v=-kAqh91UndI&feature=g-upl