How to make gable roof extend beyond the room...

Hi,

I'm using Home Designer Architectural 2014. I'm trying to make a 2nd story gable roof extend downward to a 1st floor covered deck (so it's all the same slope). I've tried adding a fake room to the side and if I get the room heights just right it will connect the two gables the way I want. But then the walls of this extra room protrude below into the porch area rather than just filling in the missing gable part. I tried using the Gable/Roof Line tool to draw the upper wall out to meet the lower gable but that doesn't seem to do anything. I hope I've described this properly. Any idea of how to do what I want here? Thanks in advance.