@segio2
In fact the usual problem is with the file size limit in FAT32, which is 4GiB (- 1 byte). In addition, Garmin devices also have limits as to how many map tiles can be contained in a single *.img file, and there is also a maximum number of *.img files that a particular device can cope with. Unlikely you will run up against either of the latter two most times, but the FAT32 limit can be easily exceeded.