I've just received a replacement Montana 680 from Garmin (a long story!). My problem is I have got City Nav 2018 maps on a 2gb sd card. I also want to load TalkyToasters 1:50000 Topo maps which (I think) are over 1mb. Is there a way I can get both these maps onto one sd card? The CN maps are locked to the card so it's not just as simple as copying the files to another card. Someone else must have come across this problem. Any ideas?