Do the seats fold down? Soul is 80lbs, and his buddy Sharky is also 80lbs. They both have plenty of room in the back of a Mazda6 with the seats folded down. More than they need, actually . . . . .
It's a very small Toyota four-door sedan. The seats fold down to get access to the trunk, but it doesn't make for a very even surface. I am just trying to picture two dogs fitting on the back seat. My one grey is a big boy and not the most coordinated dog on the planet. And he doesn't sit. He does fine by himself, but he takes up the whole seat when he lies down. I don't want to relegate a second grey to the floorboard behind my seat. I just wondered how others managed.
Just fill in the footwell space between the back of the front seats and the back seat either with pillows or something firmer - just to make a larger platform of the backseat. That gives enough room for two quite easily. Mine did fine that way in a Corolla for well over a year till we got the Rondo.