Hi Adrian,

So basically, you don't want the grid to show any partially-visible rows?

You would have to use a CreationFilter for this. Here's some quick code I whipped up which seems to work pretty well:

        public class HidePartialRows_CreationFilter : IUIElementCreationFilter
        {
            #region IUIElementCreationFilter Members

            void IUIElementCreationFilter.AfterCreateChildElements(UIElement parent)
            {
                // Check for the RowColRegionIntersectionUIElement. This is the element
                // that contains the RowUIElements (and possibly other things).
                if (parent is RowColRegionIntersectionUIElement)
                {
                    // Keep a list of elements that we want to remove. We will probably
                    // only have one element in the list, but it doesn't hurt to be extra careful. 
                    List<UIElement> elementsToRemove = new List<UIElement>();

                    // Loop through the child elements. 
                    foreach (UIElement element in parent.ChildElements)
                    {
                        // Check for RowUIElements. We don't care about any other type here, 
                        // so if it's not a RowUIElement, skip it. 
                        RowUIElement rowUIElement = element as RowUIElement;
                        if (rowUIElement == null)
                            continue;

                        // Check to see if the RowUIElement extends beyond the bottom of the parent.
                        if (rowUIElement.Rect.Bottom > parent.Rect.Bottom)
                        {
                            // This Row is clipped, so add it to the list of elements to remove. 
                            // We don't want to remove the element here directly, because that
                            // would modify the contents of the ChildElements collection, and we 
                            // are currently in a ForEach loop on that collection so it's a bad idea. 
                            elementsToRemove.Add(element);                            
                        }
                    }

                    // Remove all of the elements we marked for removal. 
                    foreach (UIElement element in elementsToRemove)
                    {
                        parent.ChildElements.Remove(element);
                    }
                }                
            }

            // Do nothing
            bool IUIElementCreationFilter.BeforeCreateChildElements(UIElement parent)
            {
                return false;
            }

            #endregion
        }