You don't need to mess with your HDs at all. All SGM was trying to say is that if you can exploit/softmod your box(es), then you can get a dash on to them and FTP into to grab the files manually from the E: Drive where they're stored, or use XBOX Saves Manager to move them.
BUT, (and I don't know if this is the case), if that game is like Burnout 3 and is signed to your HD, you'll have to find a work around to get it to work on a different HD. Reason being, that MS didn't want people just downloading 100% save games and then going on LIVE and kicking ass with them. So the gamesaves get signed to the HD they were first created on, and when transfered to a different HD the come up as "Save/profile Corrupted". There's a work around for those games (Burnout 2/3, Ninja Gaiden, though that one's a bitch), though.
But maybe RS isn't signed like that. But the fact that it doesn't support memory card copying is usually a tell-tale sign...
![unsure :unsure:](https://forums.xboxscene.org/Smileys/xs/unsure.gif)