James:
If you're modelling N440 as it is now, there seems to be plenty of material around. If my memory of Bud Davisson's article and photos is correct, the aeroplane now differs in many ways from the way it was originally configured for Hughes's planned world flight, but may well be representative of how it looked after he converted it for his personal use and as a development aircraft for the 'Spruce Goose'. In world flight guise (then NR-440, with a hyphen) the window configuration on the S-43-WH was very different from that of the standard airline S-43-W. Many cabin windows not present, presumably because long-range tanks were installed in the cabin.