Sure, the raisin is always at the center. Why? Because the edge is not observable since the universe is larger than it is old. If the universe is 13 billion years old and 14 billion years across (well, in radius from our position) then a billion years are not observable, therefore we can't see the edge.
Why? Because the center will not move in relation to all other objects, and anything beyond the edge can not be viewed.
No, the edge itself can't be viewed. The problem with looking at this through analogies (models) is that the analogy inevitibably breaks down pretty quickly. You can't infer that every element of the behavior of what is being modeled conforms to the behavior of the model.
Please explain this to me. If we can detect the early Universe (micro-wave background thermal radiation) from 14 billion years ago, why is it impossible to also detect an edge which is only 1 billion years in distance?
Curious minds would like to know....