i had no problem with 1800 x 1800 map. but in whichever game editor, change the default open ground 800 x 800 to the size of the map you copied. then when you load it, poof all is well.
i also copied a large cmak battle map, into a cmak operation file!!!! of course the units dont transfer, but this is great news.
then i ran to the SD and got those perch maps.