In EmberJS 1.13, how do I maintain child component state through collection updates?

Quite simply, is there a best practice for persisting child component state through collection updates. Here is a fiddle to demonstrate:

http://ift.tt/1W13LCI

How can I toggle item heights, add a new item, and have the existing children maintain their states? Do I need to write custom view-model management code? Is this something solved in newer versions of Ember?