I see that you found what you needed. I wanted to throw some more help towards you to help with any future HubTile uses. This link
will bring you to the documentation. If you look over to the left column and scroll down, you'll see the exp[anded node for HubTile.
Take a look at the different features and you'll be able to see the different implementations. Also, if you really wanted to customize the HubTile (for instance you tried to use VerticalContentAlignment) you can edit these properties if you edit the template in Expression Blend. To do this, right click on the control and explore the "Edit Template" option.