Add a note about SaW trailer

doc/formats/maps.md

@@ -718,6 +718,10 @@ This can be interpreted more or less the same way as the Chaos Gate maps now,
 and the `soldiers-at-war` branch contains a hacked-up implementation that kind
 of works \o/.
 
-Does the same trailer apply?
-
+Does the same trailer apply? Seemingly not. Looking at `PARIS.MAP`, there's no
+similarity at first glance.
 
+However, I did manage to track down 4 32-bit ints inside the trailer, starting
+at `0x121ad1`, which specify dimensions of the map, at least. Perhaps the
+position has moved, but some of the data is the same? It's 3320 bytes into the
+trailer.