NO Side Speakers in an atmos system?

Hey guys I hope you can answer this.
 I am looking to build a theater and have zero place to put side speakers.  I have the rears and the over heads covered plus the main front three and sub.  However my question is this, does my Pre/pro (marantz 8802a) take the signals normally sent to the side channels and send them to the back speakers if there are no side speakers?  I would hate to lose two important channels that seem more important than the rest.

Part two of this question depending on the answer from the first.

Should I use the rear speakers as side speakers?  Meaning, that I have the rear speakers hooked up to the side speaker terminals of the pre?

Thanks for your help.
Mark