I went with a 32" curved. I had to drill new holes, but I used large washers on the bottom side of the roof to keep it intact. My Z8 and been on a trailer going down the highway 80+ mph and no movement or stress marks.
I agree with everyone else. It's going depend on your preference, and where you want to mount. Here's a pic of mine. Not the best shot but it's all I have on my phone at the moment