The best setup is explained here:
http://customscreatorscollective.wordpr … 03/29/155/
You can keep TU5 so that you can buy new songs (do buy new songs from Harmonix and RBN authors, they deserve the love) and you can get TU4 for all the content.
I don’t think it’s specified in our video, but I always recommend creating a new gamer’s account with no Live connection for TU4, so you won’t be bothered with TU5 upgrades requests and your offline scores never get posted.
You are about to leave Rhythm Gaming World and access the external songs DB. While no song or file sold for commercially available videogames is hosted there and only fan generated content is allowed, Rhythm Gaming World has no direct control over the database and no files are hosted here. Alright, we had to made you aware of this, now you can visit the database!