The Anyths map is bigger than large. It was made with FE in mind and the largest label for maps there was Large, hence why you see large. Starting positions on the map are plentiful and can be used with more than 7. It has 28 start positions, and so you could effectively have 28 factions on the map. I would only recommend at most 12, to give you plenty of room to expand and give each faction some spreading room.
The map size from reading the file is 192 tiles by 128 tiles --- the standard large map size is 112 tiles by 96 tiles ---
The map is much bigger than a standard large map and has special tiles throughout to make some rather neat visuals.
