PML and scattering boundary condition in v4.3

HI,

Is it necessary to define the outer boundaries of a PML as scattering boundary layers to obtain the losses of a leaky waveguide? In v3.5, I have defined the outer boundaries as perfect electric conductors (PEC) and still obtained the correct loss values. With v4.3, if I set the outer boundaries as PECs, I get only real valued effective index solutions and not complex ones, implying that the losses are zero.

Thanks.