For future searches on the subject -- since I could not find this information anywhere -- the weights of the Porsche 19" RS Spyder center lock wheels are as follows. Measured on a digital scale with *wheel only*:

Fronts (19*8.5) = 23.1 lbs / 10.47 kg
Rears (19*11) = 26.9 lbs / 12.2 kg