microsoft metro - FlipView micro-freeze when flipping page Windows-RT -

i'm developing c# metro app use scrollviewer inside flipview flip through high definition images (2400x1800). works fine in simulator, when deploying surface rt there performance issues. when flipping through flipview first time ui freezes noticeably every time new image presented.

i have tried pre-load images bitmapimages when starting app. micro-freezes still there first time go through flipview.

i tried turn on debugsettings.enableframeratecounter, , seems memory flag doesn't increase when creating bitmapimages, increases when flipping through flipview first time leads me believe aren't loaded though created , source set?

here example project can see issue

am doing wrong?