Hello Ian,
The more tag is used (as you have already seen) for displaying custom excerpts on the archive pages.
The homepage panes are slightly different. They will display the first 55 words of a post. You can either use a custom function to control how many words are used (which alters every homepage pane).
Or, you can use the “custom excerpt” metabox found below your content editor while editing a post.
Simply enter what you would like to display, and it should reflect on the homepage panes.