Managing session files

[Gothboy]

My question has to do with managing session files in 2 versions of Pro Tools LE. I'm running 6.4 in Panther 10.3.9 on one 80GB hard drive and 5.1.1 in OS 9.2.2 on another 40GB drive. The session files are on a third audio drive and everything gets backed up to an external 160GB drive in two separate folders. One for 6.4 sessions and one for 5.1.1 sessions.
My songs started out in 5.1.1 and were backed up to an external drive that is now dead(it was replaced with the new 160GB drive just recently). My idea was to have each song in it's original 5.1.1 form kept as is in one folder, then I open them up one by one in 6.4 and work on them from there then saving these versions into the 6.4 folder on the audio drive. But every now and again I do like to go back and see how the song was before I started using it in 6. I might want to use a plug that only works in 9 or something. So I thought I could have 2 versions of each session completely unaffected by the other. But when I do that I get a version of the session that has faders that look strange and tracks that are black and grey and not the same size as when I last saved the session. I guess this is because opening a session that was worked on in 6.4 isn't backward compatible if it's opened in 5.1.1 and if I do it does something odd to the session. Plus, it's not really 2 different sessions, really....it's the same session with the same audio files even though I've attempted to put them into different folders.
Is it because they're on the same recording drive also? Is that somehow different from saving 2 different versions of the session on the external storage drive....or not? If I want to be able to have a 5.1.1 version without these difficulties should I be saving a version of the song using "Save session copy" in a PT 5 format? Is that the way to do this?

[Slim Shady]

If I want to be able to have a 5.1.1 version without these difficulties should I be saving a version of the song using "Save session copy" in a PT 5 format? Is that the way to do this?

Yes, that's the ticket!

[M.Brane]

You can never have too many backups. I keep everything. All the original sessions in their original state. If I want to experiment I work on a copy.

[Gothboy]

.....OR...while in OS9 make copies of each song, store them in the 6.4 folder, boot back into the X drive and open them up in 6.