On the contrary, they are one of the best places provided you properly remove the paint. They have a weld nut on the back and are a large thick spot of metal. It is structurally superior to regular sheet metal. Think about it, they bolt your seat down there. I don't know what the fuss is about unibody vehicles either. In this instance, the entire vehicle is the chassis and frame. It is one large ground, unlike a body-on-chassis vehicle which has isolating body mounts and requires the body of the vehicle to be grounded to the fram via ground straps.