Simscape Hydraulics, Flow rate does not go negative.

I am just starting to use the hydraulics sub-set of Simscape and have run into a problem. Perhaps a hydraulics sub-set user can help me out.

Attached is "simplehydraulicsytem.slx".

A sine wave reference supplies the position reference for a proportional valve spool position. Even though the reference swings both positive and negative, the flow rate is positive for both positive and negative reference values. Why?

What am I doing wrong? Any help wpould be appreciated.

Don Brohaugh