I hear that if you connect the pedal FC7 BEFORE you turn on the PSR SX, then turn it on, is pretty much like a computer when is booting on, if the peripheral is connected, most of the time is recognized. No need to move anything, if you notice, in the Genos, is even title those inputs....3Volume, 2(Art1), 1(Sustain) are already the default mode. This also applies to the correct/proper model of Sustain pedal.
In the PSR S and PSR SX series Pedal 1 is for the Sustain, Pedal2 is for the Volume other wise asignable.
My 2 cents
Manuel