I previously wrote up about how to use the Frequently Used Website Tabs as your default homepage in IE9 and now thanks to a MSDN post from Eric Law here is how you can expand the default number of rows that are displayed and in turn list more sites on that page.
By default, IE9 will show 2 rows of your favorite sites on the about:tabs homepage. However, you can customize IE9 to show up to 5 rows with a simple registry modification.
Inside the NewTabPage registry key, create a REG_SZ named NumRows, with a value of 2 to 5.
Eric goes one step further and provides the registry files to merge this update into your registry by downloading a file:
Many thanks to Eric for a great IE9 tip!