I currently have BIAB/RB 2008.5 Ultrapak or ultrapak plus, I can't remember what I ordered.

I'm a little short on cash for updates at this time, so I was considering buying just some of the RealPaks for my existing 2008.5 version instead of buying the upgrade 2009.5 version. is that possible? will the realpaks work with my 2008 version ok?