you can upgrade from RC to 7, whatever MS says
Have you had any sort of background or experience in the software development or QA testing process Bushfiva ?
It's not about what MS or anybody else says.
It's simply not the done thing, one of those unwritten rules.
You do not go running development releases in a production environment. It's an implied term with the developer that you should not expect to be able to get any data back from, or migrate from a development release. Just as you expect things to break on a development release.
But, each to their own. Good luck to you both ! Rather you than me !