the help for AddPatch states:
Determines the behavior of the surface in areas where its not otherwise controlled by the input. Lower numbers make the surface behave more like a stiff material, higher, more like a stiff material. That is, each span is made to more closely match the spans adjacent to it if there is no input geometry mapping to that area of the surface when the flexibility value is low. The scale is logarithmic. For example, numbers around 0.001 or 0.1 make the patch pretty stiff and numbers around 10 or 100 make the surface flexible. The default value is 1.0.
the second ‘stiff’ should be flexible I think.