I have downloaded custom topo maps from TOPO50 maps for NZ. I have opened them with google earth and transfered then to my etrex20x. I can do 1 map and it works but when I load 17 it says too many custom maps and won't display any. There is like 5 gb of space why can't it load them. I want to have a large area which I work in and don't want to connect to computer everytime to change map. Any ideas? Thanks