MahApps.Metro Flyout中的Datagrid

I am trying to create a flyout for settings using MahApps.Metro inside of a MetroWindow control using WPF. I have created the flyout and have several other radio buttons and seperators. I am now adding a datagrid to hold a list of StockSymbols used as a watch list for my application. What I am having trouble with is properly setting the datagrid so that it does not autogrow past the size of the flyout. If you add rows to the datagrid you can keep adding until it flows offscreen ouside of the window. I would like to do it so that I don't have to manually set the max Height and for it to dynamically grow as the window grows.I am trying to create a flyout for settings usi