[Mahler9th]

I suggest buying or borrowing the Puhn book.

For DIY, I think Toby's pics and approach are really helpful to study.

For the backing plates, you can use a variety of materials. Thin metals like aluminum are fine. You need to be able to scribe circles, so a compass helps, but you can use circular shapes in your shop as a template... like the bottom of a paint can.

Ideally, the backing plate will have an OD that exactly matches the ID of the inside of the rotor. This will ensure that all of the available air is available to get pumped through the rotor vanes, which is the goal. In my case, I had bought the AJ USA kit 10+ years ago, but the OD of the supplied backing plates was smaller than the ID of my rotors. I could have simple expanded that OD with a ring of aluminum attached by rivets. But I had a need for a project and some composite materials laying around. I found that one of the generic sizes for cheap metal electric oven burner covers provided a perfect mold to make composite backing plates with the OD I needed for my rotors, so that is what I used. I decided to use some left over carbon-kevlar as opposed to fiberglass.

The hub blocking plates are also intended to make sure the air goes where you want it. Some Porsche hubs are designed such that the plates are redundant, and in any case, we aren't talking about a lot of air that can get through. But I feel that if you are going to add cooling, it is worth fabbing some up depending on your hubs.

How much brake cooling one needs depends on their car's configuration and the demands of the tracks they drive. I always suggest that folks connect with others that have experience with similar cars that drive the tracks in their area to get ideas for configurations that will work.