Dear Frank

The correct solution is modify Style.

1. Press Alt+Ctrl+Shift+S to activate Style Pane which is on the right of handside
2. At the bottom of the style pane, click the Manage style button (The third button from the left) to activate Modify style dialog.
3. At the Set Default tab choose font that you want to use the default font and the size of font.
4. Set the default Aligment.
5. Choose Only in this document option, to apply these changes to the current document.
6. Click OK, and see the result.

Hope it will helpful for you.

PS: If you would like to set all changes to the template, you should choose New documents on this template.