I can reproduce this in the Diagram Editor Example.
Place 20 rectangular shapes on the drawing.
Select 19 of them and start to drag move.
All shapes will be shown on preview layer and I will get BoundsChanged events on them.
Select all 20 shapes and start to drag move.
It doesn't show the individual shapes in the preview layer, just an outer bounding rect.
It also doesn't generate BoundsChanged events for the individual shapes.

I assume this is an optimization limit.  Is there some way of controlling that?  I looked on the MoveTool and PreviewLayer but I couldn't see anything.  

We'd like that limit to be much higher.  Even with many shapes selected, we sant to see them in the move preview and get BoundsChanged events on them.

Thanks in advance,
Jason

Yes indeed by default the maximum number of shapes which are previewed when moved is 20. You can control this settings from the MaxPreviewedItems property of the drawing settings:

// increase max previewed items
drawingView.Drawing.Settings.MaxPreviewedItems = 30;

The drawing settings object also contains other settings related to drawing editing, such as the offset at which shapes are pasted, nudge tool step and other that are useful for the user. 

Best Regards,
Nevron Support Team

That's exactly what I need.  Sadly I don't think the version I'm using has that.  v. 10.6.23.12.  At least not in the same place.
Was there a different way of accomplishing that in that version?

I'll look into seeing if they want to upgrade.

Thanks in advance.

Jason

Perhaps you are using Nevron Diagram for .NET. It too supports this type of control, like this:
drawingView.PreviewManager.MaxPreviewNodesCount = 30

Best Regards,
Nevron Support Team

Opps.  I'm a goof.  I posted in the wrong forum.

You solution works great.  Thanks.

Jason