In practice, things in C are not as undefined as the ISO working group specifies them. It is virtually inconceivable that a mainstream compiler stack would do anything other than what you'd expect with example four. As for struct alignment, that's something that most C programmers should know is implementation-defined (which is one of the reasons we even have sizeof to begin with, apart from the mere convenience of it).

Sure, you've made your point, but you've made it in a ham-fisted way which doesn't really help people understand why a given undefined or implementation-defined behaviour is the way it is, and what things they should verify about the implementation in order to predict where their code will not work.