Anyone know what the map size limitations are in WED?

I thought it was 100,000 quants so you could go from +50,000 to -50,000. However, I have a map that really starts distorting bad about 30,000 quants from the center.

I see the next beta will allow a -bound parameter to be used to define the map size up to 500,000 quants. Will you actually be able to make a map this big useing WED blocks or only entities? The only reason I ask is that I now have severe distortion on my WED blocks only 30,000 quants from the center point when I thought you could go as high as +/- 50,000.