If you think a lot of applications you are going to run will depend on it and you have the room put it in root. If not you can go ahead and load it into ram. I have not loaded a lib onto a card becuase I tend to swap the couple of cards I have and would rather keep the unit storing libs and things. I am not sure if ipkg-link will take care of setting things up for libs or not. I would assume so. You might as well try and let us know.
If that makes you uncomfortable you can always wait untill someone who knows more on the issue posts