I have it most of the way there, but I've encountered an issue with the ParentLiCssClass property. For this particular menu, the CSS Class for li with child pages needs to be "has-dropdown". The problem I have is that the "has-dropdown" class is being applied to all of the li elements that have child pages, even if none of the child pages are going to be rendered (because their settings are not marked "include in menu", and perhaps other reasons [hide, security, etc.]).
My initial thought is that this could be a bug in the FlexMenu implementation, unless there's something I'm missing?