On our NH (can't speak for the others for certain), the main compartment is sealed, with hefty locking snaps. The trap door would be closed by gravity if it got over on its side. I think the only way you'd get spillage the whole thing came unbolted from the floor during a rollover.Regarding the spillage, I was more curious as to the risk of the solid waste spilling. I assumed the liquids would spill. Do you think the hinged covers would pretty much keep the solids contained or at least help to minimize spillage?