I was wrong, the spacers are 15mm, which you can double up to 30mm. (Corrected above.)
Works great, and is perfect with my clutchstop. I wasn't able to move the seat back, but I was able to raise the front of the seat up to the max, which puts my shoulders farther back, so I'm comfy, now.
FYI: Roger checked, Porsche says there are ~170 in stock. There used to be a automatic brake pedal sized version, but that is NLA.
vertical pedal adjustment
brake pedal
clutch pedal
15 MM
928 423 207 00 spacer plate
900 067 057 02 pan-head screw M8 X 20
N 042 131 1 shake-proof washer
30MM
900 067 081 02 pan-head screw M8 X 35