br: If the math works, it should work ...in a pinch. If you think like me, the tent is only necessary if the weather is too cold or it is wet. I sleep outside otherwise. When four people sleep in the same tent, alternating head-foot directions helps, too.
In your case, one or two could sleep outside, and all four only inside in a pinch.
However, fitting 80 inches of pads into 78 means that some sleeping bags will be against the tent walls. If it is wet, the bags could get wet.
