When creating a double-sided material using Stingray PBS, you must enable the Double Sided attribute on both the object's shape node and the Stingray PBS's Standard Base node. This ensures that your object renders with the correct lighting in Maya. If you only enable the former, the lighting may not be correct for the shader.
After assigning a Stingray PBS material to your object, do as follows:
In its Attribute Editor, select Double Sided.