The 610 can have two user maps in internal storage (gmapprom.img, gmapsupp.img) and one on the SD card (gmapsupp.img). None of those maps can be larger than 2GB minus 1 Byte (2,147,483,647 Bytes) in size due to the 610 using FAT for its file system instead of FAT32. With that said, if I understand what you're trying to do, you want as much of Europe as possible on the 610 as well as your home country?

Set your home country's map as gmapprom.img. That way it's always available. Europe will need to be split into two images. One of them will go onto the device as gmapsupp.img and the other onto the SD card, also as gmapsupp.img. Hopefully it all fits.