When scrolling up in a virtual grid, the rows "above" seems to not be kept or loaded like when scrolling down, and it takes a while before they gets "loaded" and shown. This behaviour is not very user friendly and should be corrected. I can accept a certain time of delay when doing large scrolls using the scrollbar, but not when doing a scroll-wheen or page-up scroll.
Unless I missed something in the grid properties? I got the PageSize set.