Head unit with four speaker output wired two speakers

I purchased a head unit to replace the old stereo unit in my RV.  The old unit was a two-channel stereo unit and there are only two stock speakers. The new head unit (like most) has 4 speaker outputs.  Can I bridge the front and rear speaker together to one speaker?  Like left front and left rear to the left speaker and right front and right rear to the right speaker?  Or do I just not connect rear speakers and fade forward in the controls 100%. I suppose I could just add the rear speakers, but wire routing in the trailer is a real PITA. I would prefer not to.

I want to take you in advance for your advice.