Small update: my player page can now read modules made with DnFamiTracker 0.5.x.x and export them to Dn 0.4.0.1 files without having to go through FamiTracker's text export/import.
Small lifehack: if you don't want to use my website, you can remove the first 3 bytes of a 0.5.x.x module and make it instantly compatible with 0.4.0.1