I am into my third set of Porterfields. The first thing I noticed about them in comparing them side to side with a full original pad is that the liner is thinner then the stock pads.
That considered, I'm questioning the "most have shaved them down" comment for accuracy.
It is a false narrative here.
I will say that I also question the value on a street car.
Yes the r4s is the street compound but I don't see them as better in any way then your regular, run of the mill "semi-metallic" compound especially considering the differences in cost.
I don't see them as having better stopping distances and I don't drive hard enough apparently to use the heat fade properties.
Just my observations and there may be some advantages to using them if you are a serious auto-crosser that drives the car to the event.
I see Vintage Trans Am racers (which I am not) going through two or three rotors and pads just in practice sessions. So you can make your own judgements on that scenario yourself?
I can't run out and mic' the thicknesses for you but the stock pads in the shop are roughly 3/8" thick wearas the Porterfield's are roughly 5/16" thick out of the box.
Make sure that your pistons are fully seated. Sometimes internally they develop a ridge that stops the piston from fully seating. That will make the pads seem too thick new for sure. Been there...done that.
This grey hair and bumps on my head were earned by hard knocks. It isn't necessarily a universal requirement for others though?