GCVirtualController -- Unable to customize appearance of analog sticks with a custom UIBezierPath

GCVirtualController supports setting a UIBezierPath for configuring controller elements. This seems to work fine for things like A/B/X/Y buttons but it seems to be silently ignored when trying to set against the analog stick elements.

This doesn't seem to be a documented limitation. Is this just a bug in GCVirtualController or an intentional limitation?