My brain remembers seeing a website that sold upgraded vented stainless steel pistons for the factory Cobra PBR calipers. Any chance anyone remembers who it was? My way back machine appears to be broken.
I found where I found them, but they look like they are no longer made in the 40x40 size. Here is a video from AP racing about piston material and design. Starts at 3:40 if you have free time at work like me : ) https://youtu.be/iduAqKqiQXs