Hi in the demo site you guys have specified the size of the image and it fits well in the space. I’ve found a work around. If I use full or empty the image takes up the full width of the column, but then I can use the design options to a 20px of margin to the left and right of the image. this gives me what I’m looking for. Not sure if its the best way of doing it but looks ok.
I also contacted the makers of WP bakery and it looks like retina image are not supported at a specified size anyway.