You can use taco-mans tool located
here. You enter 2 in game locations and then the pixel location and it gets you a very good zonerect.
I normally open the log txt, take about 10 strings of locs from the top and 10 strings from around the middle and make a new log txt then Render that out to SVG, then PNG, then overlay it on top of my map in photoshop and change the color to red and resize/posistion it so it over-lays on top of the outline.. Then I use the locs from the top of those 2 strings and the corresponding pixel location and feed them into taco-mans calculator. Its a pita but it works and this way you can resize the map as mush as you want as long as you keep it in the same proportion (locked aspect).