You guys with Navionics card, does it also cover ohio and mississippi river bottom topo? Are they on SE card or which one?What is the main difference between the 3 brands of navigation cards available. So, if you have to leave the Navionics card in the slot to see bottom graduations from Navionics, are u saying u have to insert ur extra blank card in there to save the waypoints? Sorry, I'm not understanding.