Very odd, my post in answer to bikeguyjoe is gone, anyways....Mike is correct, I just finished putting it together and I had to enlarge the two bolt holes on the inner edge but just a very tiny amount. Yes it is made out of metal but I used side snips/side cutters.
I left the centre like you said bikeguy joe because it really is hard to cut.
On the brighter side, I like the fact that it is metal. The perforations will compress into place and this may last for awhile. Also sanded down my rusty muffler and gave it a nice flat black paint job with BBQ paint.