Thank you for the detailed response to my question -- that was what I was looking for!

I don't think body contact is any more required in shadow position than it is in facing position.

I've seen good dancing done in contact, and for shadow the best example currently in my mind was done with an arm connection only.

I think what's more important than the spacing of the bodies is the stability of their relationship. If you can maintain a fixed, or intentionally evolving spacing, then it's fine to be apart. If you keep making unintentional or innapropriate changes relative to each other, you are going to have problems no matter if you are nominally in contact or not.