Ryan, on the Post Setup page you can add a PlaceHolder, you should see it in the Execution queue pane. Add 1 package at a time to the list, you may be able to get a place holder between each one and you can move items up or down. Hover the cursor over the placeholer in the queue and parameters to see its notes. I dont know how the placeholder actually works because i never add installers but its worth a go.