No, Sp/Sx is contraflow and that's not attractive to the public. Sx/Sp is synflow. That's actually how I decided on Sp/Sx over vice versa.
Synflow:
So/Sx
Sx/Sp
Sp/So
As you can see, there's only one pairing with one each. The contraflow are those inverted:
Sx/So
Sp/Sx
So/Sp