Steve
But, if you make a rectangle when selecting the area you want to make and have the short side 1800km, depending where you are on the globe you can make the other side (E/W) longer, say for argument sake 2000km. When you apply the Mercator projection and correct for latitude it will make the map square (if you have the correct aspect ratio to start with) but the area you cover will be the same (in degree coverage and km) and eliminate some of the stretching the Mercator projection introduces. Now as I said all of this depends where you are on the globe, the closer you are to the equator the less distortion. I found a source that shows how much the Mercator projection distorts for a given latitude. GM automatically resizes your maps as a function of latitude when you resize using the Mercator option. Last night I remade the original CFS3 theater (14 degrees N/S and and 21 degrees E/W just like the original) resized and made the msh files. The pixel size is larger than the original CFS3 theater, so resizing the LCF will need to happen.
Need to install and see what happens later today. If all goes well then it is a matter of some math (trig -did I ever tell you that I hate trig) to resize the maps as needed. I had to edit the ers file but it ran as expected. Hopefully I will be able to have success and we can have as close to an 1860 by 1860 theater as possible.
Regardless you are correct 1860 km is not much in the Pacific. But when you model Midway for instance, the distances were not great since the range of the aircraft from the carriers was quite limited, what about 500 mile radius SBD and the Aichi 400 miles? Now flying form Tinian to Japan 2500 km so no joy there.