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Springtomize prolly can do this...I don't use it any more so I can't check but its worth investigating. I know you can disable dock with it. I also know you can specify how many rows you want to use. Based on this, I assume you can achieve this setup with springtomize.
 
I use Springtomize to do exactly this. Springtomize->Dock->Hide Dock and Springtomize->Icons->Additional Row.
 
Hmm. I don't like springtomize. Something's about having 100 plus dylibs rubs me the wrong way. I have switched to flex.
 
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