So, net result, yes. (?) But since Wilbur first calculates for the entire surface it 1) may take a while, and 2) may consume memory, especially for the undo file. Correct?

I presume that if I save a file as an MDR that I can later make a grayscale BMP, JPEG, or PNG to load into GIMP? Is MDR Wilbur's native filetype, or something else?