I am trying to understand the rendering of blocks on the alloy templates demo page. http://alloy75.demo.episerver.com/

Especially the "tetris effect" mentioned in this article http://world.episerver.com/Articles/Items/Alloy-Templates-for-EPiServer-CMS-7/

I have a block that I would like to render as full page width, when "alone" and as half page with when I have one other block in my content area. 

I have my contentarea:

<EPiServer:Property runat="server" PropertyName="ContentArea" CssClass="contentarea-fullwidth" DisplayMissingMessage="false">
<RenderSettings Tag="block block-wide" />
</EPiServer:Property>

And I have created 2 different templates (one block type), with 2 different tags: one for half page width and one for full page width.

And I am using the Initialization module (ClassFactoryInitialization : IInitializableModule) from alloy templates, together with the webcontrol SitePropertyContentAreaControl : PropertyContentAreaControl, also from the alloy templates.

But I can't get it to work. If I place 3 blocks in the content area I would like to get 2 half page width and 1 full page width. But they are all the same. (Depending of what tags a write in the renderoptions of the content area) 

What am I missing?