When a RestrictionZone is used the RadWindows are not positioned correctly in all cases. When the number of windows is low (e.g. below approximately 6) the dimensions set to the RadWindows are not optimal. In some cases not all the available viewport is filled even if the number of popups matches the needed (e.g. 6 instances should be able to cover the viewport, but they cover about 2/3 of its height).