Ah, I see. So please correct me if I’m wrong: basically the only things I can do to stop the plugin from downloading both versions of the image at once (like this https://www.dropbox.com/s/hczxqm3zyg89tfz/network.jpg?dl=0) is to either:
1. Make the thumbnails on the page smaller – increase the number of columns, decrease the “Select Min Thumbnail Width” setting, play around with margins etc.
2. Or, without messing with the layout, set the medium image to something bigger than 300×300 and regenerate thumbnails.
Or is there a simpler solution that I’m overlooking?