How to Expand WPF Ribbon Group

Hi,

I have two questions regarding WPF Ribbbon 

1) I'm working on a wpf application where i have many buttons in a Ribbon Group so I want to Hide few rarely used buttons in a drop down like it is in AUTOCAD(refer to the attached screenshot). Kindly help me find a solution on how to implement Dropdown in Ribbon Group

2) How to style RibbonSplitButton and  make the selected Item in the dropdown to appear beside the SplitButton.

Thanks in advance.