c# - WPF RibbonApplicationMenu Cannot Set Drop Down Height -

using microsoft ribbon control in wpf application , using application menu this:

<r:ribbon.applicationmenu>     <r:ribbonapplicationmenu         <r:ribbonapplicationsplitmenuitem header="item 1">             <r:ribbonapplicationsplitmenuitem.items>                 <r:ribbonapplicationmenuitem header="sub item 1" />                 <r:ribbonapplicationmenuitem header="sub item 2" />                 <r:ribbonapplicationmenuitem header="sub item 3" />                 <r:ribbonapplicationmenuitem header="sub item 4" />                 <r:ribbonapplicationmenuitem header="sub item 5" />                 <r:ribbonapplicationmenuitem header="sub item 6" />                 <r:ribbonapplicationmenuitem header="sub item 7" />                 <r:ribbonapplicationmenuitem header="sub item 8" />                 <r:ribbonapplicationmenuitem header="sub item 9" />             </r:ribbonapplicationsplitmenuitem.items>         </r:ribbonapplicationsplitmenuitem>         <r:ribbonapplicationsplitmenuitem header="item 2" />     </r:ribbonapplicationmenu> </r:ribbon.applicationmenu> 

this shortened version images,commands, tooltips etc properties removed keep code shorter.

the problem there 2 items 1 item has many sub items. these sub items appear 2 items scroll arrows. annoying tried using dropdownheight property on application menu makes no difference. height size needed 2 main items.

isn't dropdownheight supposed set height regardless?