I changed my home page content (as found in html/includes/define_main_page.php) to be a Banner Manager item instead. Why? That way I can automate changes in content by date. I can also track hits if I'm using an image.

I though I'd post the code, just in case anyone else is interested.

I switched the "Header Position 3" Banner from being at the top of the page, to being part of the main content.

1. copy /includes/templates/template_default/common/tpl_main_page.php to your override folder.

2. comment out the following code, at around line 99

<?php
if (SHOW_BANNERS_GROUP_SET3 != '' && $banner = zen_banner_exists('dynamic', SHOW_BANNERS_GROUP_SET3)) {
if ($banner->RecordCount() > 0) {
?>
<div id="bannerThree" class="banners"><?php echo zen_display_banner('static', $banner); ?></div>
<?php
}
}
?>

3. copy /includes/templates/template_default/templates/tpl_index_default.php to your override folder. Check that it's not already there in case you've already made some changes!

4. comment out where the home page looks for the define page, at around line 33:
<?php if (DEFINE_MAIN_PAGE_STATUS >= 1 and DEFINE_MAIN_PAGE_STATUS <= 2) { ?>
<?php
/**
* get the Define Main Page Text
*/
?>
<div id="indexDefaultMainContent" class="content"><?php require($define_page); ?></div>
<?php } ?>


5. add the Banner Manager code in the same place
<?php
if (SHOW_BANNERS_GROUP_SET3 != '' && $banner = zen_banner_exists('dynamic', SHOW_BANNERS_GROUP_SET3)) {
if ($banner->RecordCount() > 0) {
?>
<div id="bannerThree" class="banners"><?php echo zen_display_banner('static', $banner); ?></div>
<?php
}
}
?>


6. Load a banner in Tools>Banner Manager and activate it in "Header Position 3" in Configuration>Layout Settings

That's that. You might also want to add the orginal stylesheet tags to your banner, in which case the opening tag for it should be...
[SCR]<div id="bannerThree indexDefaultMainContent" class="content">[/SCR]