No matter what you do,
ALWAYS, ALWAYS, ALWAYS, use some sort of backing plate. Even a home made thing will be better than none at all. They are extremely important, for both cooling, and heavy debris. I'm basing this on a lot of years professional brake work experience. The reason these aftermarket companies tell you not to put them, is purely cosmetic. They believe it, "Dirties" their product. I'm interested in making this upgrade. I will get most of my parts from a private source. Please, though just make sure you put on backing plates on whatever you build. They are very effective for a long list of reasons, and I could not stress it more.