I keep a 2GB card in mine for screen shots and storing my *.usr file (waypoints). I also periodically copy the *.usr file to my computer so I have 2 backups of my waypoint file. As I mark new waypoints I can copy the updated file in the unit to the card so my backup is current. I had a map card in my old Lowrance and could store the waypoint file on the map card. There is usually enough room left on them to do this but I don't know if you can with the new ones. Of course you have to be careful you don't delete the map file.
Fair Winds and Following Seas
Bill H. PTC USN Ret
Chesapeake, Va