Pete, this is my approach that avoids having to export the Header as a separate PNG; the file does it for you.
Provided you group all the elements together and give them a filename of "banner", the Header can be as simple or as complex as you choose.
Also I have removed the need for a !Fixed layer so the design of the Header is more intuitive and it can be anywhere on the Banner Layer.
The final Header size can be the width of the page but scaling up to a Placeholder width of 3,000 px width probably means it should be at least 1,500 px.
Note, for the Header to render across the page, the Website must not clip to the page edge.
I am sure there is a lot of scope for improving the CSS in the Placeholder but, for present, it works and can be experimented with.
Banner.web
Acorn
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