Hi Tony,
I did expect the coefficient of friction to be less but not to this extent, and I understand the theory of having holes/slots/grooves. Interestingly a lot of performance discs are grooved and don't have holes all the way through, I did this with my carbon steel discs. I don't know if you've seen these Chinese discs but the slots taper from 10mm to 7mm wide and the notches are aproximately 20mm wide by 8mm deep, all that is quite a lot.
I did a lot of deglazing of the pads with 120 grit paper and then washed them with "Electroclean", it's for cleaning electric motors/brushes and dries without residue. I didn't want any carbon steel particles embeded in the old pads to transfer to the stainless steel discs.
Regards, Russell