I was able to make one custom map by using Basecamp 3.0.2 to import a kzm file from Google Earth. Now I am trying to add another, but I get an error message saying "cannot import". I've tried reducing the file size (I understand 3 MB is the limit and I've tried much much less than that) and also the image size, keeping below 1K by 1K. Tried KZM and KML. Tried setting opacity to 100%. Tried setting drawing order to 50 or 51. Tried coping the file into the \Garmin\CustomMaps folder on my Dakota. Tried changing the file name to remove the spaces. Tried everything I can think of.
But hey, here's an idea. How about if Basecamp gives me a tiny little clue about why it cannot import a file. For example, if the file size is too big, say "cannot import the file because the JPG image exceeds the maximum size of 3 MB." Is that so hard? I don't think so. One of the main reasons I bought the Dakota 20 was to use custom maps. Between the sparse documentation and buggy software, that feature is barely usable.