Thanks ionC2 will try this and report back as to whether this works under Cocoonjs 2 beta.
Neondev the window size is set at 1280 x 720 which is a 16:9 ratio but the background is much wider to allow for scrolling and 960 deep to fill the screen under different resolutions including 1280 x 768 16:10 ratio and1280 x 960 4:3 ratio. These are the 3 main aspect ratios for modern phones and tablets.