Good point about the pixels Kacey. I assume that when the city slices are handed out they will all be the same resolution. I'm probably going to blow mine up to 200% to work on it (making the obvious allowances for doubling the linear scale), and then reduce it again before uploading it, so that it arrives here exactly the same shape and size as I was given it.
Does that sound like a reasonable solution - to return things the same size as sent?
I also have another question for everyone generally:
What exactly is the 'normal' direction of the light in a top down map? I know what it is for me, but I don't use PS like the majority of the rest of you, and would hate to put a shadow on a tower that was at odds with all the shadows you were putting on your towers!