I am temporarily only using two front speakers with my 990 - no surrounds or center right now.(I am slowly upgrading my system). The "speaker Size" setup menue does not let me choose that as an option. I have to pretend to have either a center speaker or rear speakers.

Is there any way around this or am I missing something?

Like you, for now I'm only using two front speakers. The speaker size menu does not allow me to choose "none" for the rears but it does allow me to choose "none" for the center. I'm not sure why this is or what it means. I suppose it means I'm unable to redirect the rear signals to the front and I'm ok with that.