Datagroup (virtual layout) + itemrenderer: slow scrolling?

Question

Hi all,
In one of our solutions, I'm showing a list that can contain two types of rows.
Since the list can be quite long, I made it as following.
- I have a DataGroup with a custom item renderer.
- the DataGroup has a vertical layout
- it uses virtualization (so the rows are only rendered when they are visible)
It all works flawless:
if you click the arrows of the scrollbar, it's lightning fast.
If you use you mouse scrollwheel, it's lightning fast.
Only, when you drag the scrollbar and move it up and down, the rendering is somewhat slow and delayed.
Not much, but a reasonable delay that is visible (the list is empty for a split second before it's rendered).
Since it works fast when you scroll the mousewheel (which is also a pretty fast way of scrolling), which indicates that the itemrenderer can be fast, I am wondering if I'm missing something.
Do any of you guys have experience with DataGroup lists in combination with a custom item renderer and virtualization?
Should I use other components maybe?
Any input is welcome, thanks in advance.
Ivy
PS Since the itemrenderer is recycled, it works as following: it initialises both the types of rows (as said, there are only two different type of rows) and makes them both invisible. Then, when the data setter is called, the correct type of row is putted back to visible, and is filled with the correct data. This method is suggested in this series by Peter Ent, on Adobe Devnet.

Answer 1

from the API docs
A container using a virtual layout that contains few children whose sizes vary widely can respond poorly to interactive scrolling using the scroll thumb. No performance degradation occurs when scrolling using the scroll arrows or by clicking in the scroll track. Responsiveness improves as the variation in size decreases or the number of children increases.
I have a similar issue and would love to hear of any work arounds