When you mention xC5, would it be because you consider that as a minimum fixpack level for acceptable stability?
If yes, I totally disagree... But that would be a side discussion.
You have to obey the license of the version you use. That means you cannot use a feature made available on version N+1 in version N.I understand that morally it doesn't sound bad (you bought the software and pay support...) but as I understand it, it would be a license violation :(