I bought a set of Porterfield R4 pads for the front, but I see now that Tirerack is offering a limited selection of track pads for the rear (and only the rear). So I was curious to the guys who have tracked their cars, how did the rear pads fair? I have a 2-day open track event at the end of June. I am hoping to spend at least 3 hours lapping each day. How will the OEM pads hold up with NT01's on the car? Is it worth buying a set of rear track pads? I'd hate to chew thru the rear street pads for no good reason.