Header image size - iPad

I have been looking at Displaying Images and Documents | AppSheet Help Center and have a question. Appsheet appears to set the maximum width of an image to 600 pixels but in a detail view, when using a Main Image, I am expecting the image to span the entire width of the view. The text box that overlays this, the Header Column, is 736px but the image is resized to 600px even though it is in a container that is bigger.

The result is that the header text stretches beyond the boundary of the image and just looks poor (white text on a white background) but nothing I do with the header image will result in something wider than 600px. But I guess this is expected but if I cannot control the width of the header text either, not sure how I overcome this.

Anyone with a good trick here?

div.SlideshowPage_header 768 x 185.16
div.SlideshowPage_header-image 768 x 185.16
img.ImageWithSpinner_image 600 x 135
div.SlideshowPage_header-item 768 x 185.16
span.TestTypeDisplay_text 661.8 x174

I know it is bad form to respond to your own email but I have realised that there re many issues with an iPad in portrait mode. It looks like the device type / screen resolution is not detected correctly and the very little is sized correctly. Landscape is fine.