Hm, I just measured my insane map by placing a ship with enough range in the upper left corner of the map and ctrl-hover over the the hex in the upper left and middle right corner.
For the upper left corner it says Distance 380 moves, for the middle right corner Distance 381 moves what I don't understand since for a symmetrical hex map both distances must be the same ... ?
Anyway, that would mean despite the xml entry of 380 for HexSectorSize the real size must be 381 or 382 hexes, and it means the number of hex fields at the edge of the map from one end to the other or from the center hex to either edge of the map (including the center hex). That's 434,341 or 436,627 sectors altogether (the formula is 1 + (1 + (r - 1) / 2 * ( r - 1 ) * 6 with r = radius of the map in hexes, giving 1 sector for radius 1, 1 + 6 = 7 sectors for radius 2, 1 + 6 + 12 = 19 sectors for radius 3 etc.
With every new radius R the overall sector count increases by (R - 1)*6 hexes.
And now I hope I didn't miscalculate