Then another method would have to be used, hum..
I personally never go over 800x800 window size inside C2, and I design with that size (on higher resolutions, due to the way C2 scales up and down, the assets quality is not lost), that is why I suggested first to set the window size proprieties to 800, 800*actual_height/actual_width ; and set the layout scale to 800/actual_width (actual height and actual width being the height and width you used during the developpement), if some hud elements appears weird, the layer scale rate could help adjust that I think, but not 100% sure