I wrote a Max5 to Max4 patch converter in SuperCollider. The reason was to get more people to install SuperCollider. So this is software with a hidden agenda.
Download it here. See the readme for installation instructions and info on how the conversion works.
It can also be used to generate, examine, manipulate and process Max5 patches in different ways. Below are some screenshots of patches from the max-examples folder that I manipulated using this class. They might look strange but are fully functional. I just did things like add curly segments to all the patchlines.