[A.J. Holz]

I haven't tried this to verify it, but you *should* be able to:

1.) Use CatoBase v4 for your OOTP4 files, import whatever v4 files you have into the CatoBase database (I just like saying that).
2.) Once you're done with the v4 files, open the database file in CatoBase version 5.3.1. It should upgrade your existing data and allow you to add subsequent seasons of OOTP5 data.

It's supposed to work, but I've never tried it. This would save you the hassle of upgrading all of your v4 end-of-season files to v5.