With Gantry, there's no need to duplicate the template!
Extensions > Template Manager > Defaults > Menu Items >
The Defaults option lets you setup and configure all the parameters for the template. These are then used for every page on your site. If you have a need to have one or many of these parameters set to a different value for a specific menu item, choose the “Menu Items” toggle above.
Choose your Menu Item and apply the pre-sets as you like.
Pretty cool, huh?
