Create single .xib for Universal app in Interface Builder? (iOS)

Question

Apologies if this is a silly question, but I've done some googling and searched SO and haven't found anyone asking this exact question.

I have been doing iOS development for some time now, but I am completely new to the Interface Builder. What I want to know is this: is there any way to just create ONE .xib file and then use it for both iPhone and iPad in a Universal application?

It seems silly to me to have to create them separately; why do twice the work laying something out more than once in Interface Builder when I could do it once (with minor adjustments for screen size) in code?

Please let me know if I'm missing/misunderstanding something here. Like I said, I'm a complete Interface Builder newbie :)

EDIT: I have submitted non-interface-builder games to the App Store in the past where the iPhone and iPad versions were identical, so I'm not concerned with making the game look/feel different on each device. I intend for them to look exactly the same, aside from some slight positioning changes due to the difference in aspect ratio.