Well, I found this little nugget out. When taking a project from FCP 7 back to FCP 6.0.5 via XML, v4...everything works BUT...Boris Title 3D. Not if there is just one or two...but many back to back. My lower thirds come up fine and render fine, but when I try to render the 20 Title 3D cards I have in the credits...FCP crashes. Just putting the playhead over them crashes the system...or loading the sequence I built them in. Has something to do with having that many back to back.
But this isn't specific to FCP7>FCP 6. Apparently this is an ongoing issue...happened with FCP 6>FCP 5 as well.
So I had to open the project in FCP 7 off my secondary boot drive...make the changes to the credits, export them as an Animation codec, then bring that file into FCP 6.0.5 and tag it on the end.
Wondered what was happening. 4 projects all XML'd fine, but when I hit the credits...YOINK! Crash.
I have noticed some strange behavior in Color when Boris red comps are part of a seq sent from FCP7.
Only some of the layers show up. The rest are flagged offline, no crashing.
Well Red is not approved for FCP7 anyway.
Other than that most of my stuff seems to work very well on 2 systems (testing only). One on MBP complete uninstall (5hrs). One on a new 8core MP, just update. Both run fine so far. I am loading old project with hundreds of clips, to see if I can break something.
Boris never worked good with XML as they put their own encoded stuff in there which requires an external app 'Boris' plus FCP to communicate and sort out things when the files are 'reconnected'
So if you plan to exchange by XML be VERY careful with Boris, better don't use it.