The most crazy thing about new PIM is I improved the base compression keeping FULL compatibility.
As a proof, download packed 'fp.log':
fp.pim (566 KB ! )
and unpack it with current or older version of PIM... and verify contents!
In addition, I will add a new EXE filter. So, you will not be able to extract new PIM archives with EXE files with older versions.
However, with new version you can extract older PIM files, of course.