Personally, I'd consider putting on the lath over the curb when putting in the pan's setting bed. The lath can help to tie the pan and the curb together if you use that technique. I like to form the lath into sort of a question mark shape, with a tail into the pan. The TCNA guidelines call for a reinforced mudbed. WHen you form the cup shape to fit over the curb, overbend it a little so it has a bit of spring to it, which helps to hold it in place. Only put fasteners low down on the outside - never any in the top or inside through the liner.