So from what Hangdog42 says, it can be done, but from Nirvanix, it may be hard, and not so easy. So easier would be to download the RH9.1 iso images, even if it seem to be hard to find a moment where their servers are not too busy. I tried few times these days but it always fails.
A related question is does somone knows about linuxfromscratch. Is it a solution for non "newbies" ??