Cornetnut:

I did not cut the $5.00 lip I bought. I used the flange where some cut it off. Mine fit very well. I also did not paint the one I have. I cleaned it good and used a plastic preserver. My car is black and I liked the contrast I got just by using the preserver. I also ran it at 105mph for 30 min. to make sure that I had no breakage or loosening of the mounting.

Oh, the SRT6 already has a lip!.
I'm sure what ever you do will turn out fine, just look at it from all angles before you cut it.