Just hit rebuild again, it still has the same old fussiness as the other editors.
Also when you are happy with the 512 x 512 bmp map in the editor clip board then divide it up into the (4) 256 x 256 maps. (map0, map1, map2, map3).
As for takeoff positions
1)what was the first shape added to your terrain.
2)if it was a (vehicle, port, airfield) that had a tower with it, did you remove the original tower at grid 10.24 / 10.24.
Pokie