Virtualized Layouts are nice, but I find that they often feel a bit "chunky" due to the "tightness" of the virtual range. This could be improved by increasing the range - one or two steps ahead (and behind) would often be enough to improve the "responsiveness" of the list, especially when external resources (like images) need to be loaded.
How could one implement this?
Your starting spot should probably be DataGroup.getVirtualElementAt(...)
It's a complicated subject, and you'd probably have to define both your own custom layout to deal with the additional virtualisation behaviour, and some elements of the DataGroup to prevent the IRs from being garbage collected too soon.
You are running a fair risk though... this isn't an easy route!