I am making a prom dress for my daughter and would like to sew in some bra cups. I bought the molded bra cups, but the only directions on them say to follow pattern instructions. The pattern I am using does not call for them though. The pattern I am using for the top of the dress is Butterick 3520 It will be fully lined, so I thought that I would have her try on the lining and pin the cups in place. Would I then sew them all around? Or tack them in strategic spots?