Modals with long content can have their submit buttons pushed well below the bottom of the screen (e.g. project people tab -> add someone when there are many languages). The footer of the modal should be always visible on screen, with the central content scrollable if it would push the footer off the bottom of the screen.
example: Project people manage permissions dialog.
Check other dialogs for breakage. e.g.: File upload dialog.
Make sure small dialogs still look good.