I'm using a 60Cx.
Maps downloaded from GPS depot for Nevada and Arizona show all appropriate data.
Sending data to my Garmin with MapSource, along the borders of states, I find that one states data will over write the other states data for the same sector and do so in such a manner that I can not control it. Map segments of one state may have blank areas over the border for the adjacent state's data.
Here is a specific example using the Arizona topo and the Nevada topo:
Nevada topo segments Topo K-7 and L-7 the Gold Butte areas west of the Arizona border, south of I-15, north of a branch of Lake Mead.
Arizona topo segment B-1 that overlaps Nevada L-7
The Nevada L-7 has all the topo data, the Arizona B-1 is blank for the Nevada section of the map segment. The Arizona segment always trumps the Nevada segment when these are transferred to the device so that Nevada data is replaced with the Arizona non data.
I see no way in MapSource to arrange segments or prioritize segments such that the Nevada data trumps the Arizona non data for that area.
There appears to be no way to nudge MapSource to use the Nevada segment and always applies the Arizona blank segment. Any ideas for a fix for this since there may be other blank areas in a stitched download with no data and I'd like to find that out before hitting the back roads.