scm_from_double (top_curve.control_[2][Y_AXIS]),
scm_from_double (top_curve.control_[3][X_AXIS]),
scm_from_double (top_curve.control_[3][Y_AXIS]),
scm_from_double (top_curve.control_[2][Y_AXIS]),
scm_from_double (top_curve.control_[3][X_AXIS]),
scm_from_double (top_curve.control_[3][Y_AXIS]),