Just to give everyone an update here, the Porterfield R4S failed on me only a couple of months in. Ended up cracking a pad during a canyon run from over heating the pad. I would not recommend it for a heavy car with R compound tires.
Too bad because I really enjoyed them as a street pad, but definitely not something you can be aggressive with in high speed twisty roads.
Ultimately I lost confidence in my braking about half way into the run and the pad lost a small chunk of pad material during the process. It seems like when these pads exceed their temperature rating, they become very inconsistent. High initial bite followed by very mediocre braking behavior.
I am going to have to step up to a race pad and deal with dirty wheels every other day, but I will learn to live with it to avoid having a miscalculation at higher sustained speeds