kovidgoyal - Thank you for your answer! I tried to do the insert image, with full screen & aspect ratio checked and with body and @page margins set to zero.
When I then open the epub file in calibre the image still looks the same - it does not go to the edge of the reader panel as I expected. And likewise, does not convert to a pdf with full page image. Sorry, I am obviously missing something here.
Here is my updated epub html file for reference:
<?xml version='1.0' encoding='utf-8'?>
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<title>Unknown</title>
<style type="text/css">
body { margin:0; padding:0; overflow:hidden }
@page {
margin-bottom: 0pt;
margin-top: 0pt
margin-left: 0pt;
margin-right: 0pt
}
</style>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<link href="stylesheet.css" rel="stylesheet" type="text/css"/>
<link href="page_styles.css" rel="stylesheet" type="text/css"/>
</head>
<body class="calibre">
<div style="page-break-before:always; page-break-after:always; page-break-inside:avoid"><svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="100%" height="100%" viewBox="0 0 889 1186" preserveAspectRatio="xMidYMid meet"><image width="889" height="1186" xlink:href="images/CC3.jpeg"/></svg></div>
</body></html>