As far as I can tell, the only pin on the Xadow flex cable that you can do PWM with (at least using the arduino IDE) is SCL. (And if you screw up and plug in the breakout board backward, SCL will show up on the pin labeled A5).
You can also do PWM on the green LED, but that isn't routed to the flex cable.
So that sucks, especially since Xadow is billed as having 7 PWM channels (which the underlying Atmel chip does indeed have).
