Hi, this is awesome tutorial / guide.
( http://wordpress.org/support/topic/activate-from-worpress-menu-iem?replies=2 )
I use Form lightbox with SS Downloads in order to collect an email address in return for a file download and display it via the top navigation in an modul / overlay / popup.
The Form lightbox works well when embedding the shortcode for the SS Downloads plugin. see scereenshot (1) Howecer, Once you click on Submit, another Form lightbox needs to open like nuber (2)
You can also see the SS Downlaods form embedded in the link below, but, when you us it once, the download page will seem to work for the Form Lightbox version too.