Kitting and free goods

I am trying to use kitting with free goods with the WMS system.  We build assemblies which would be the finished product and depending on customer and order quantity, free goods are associated.  For example, if i order 4 assemblies, i get 1 free good, if i order 8 assemblies, i get 2 free goods.  Has anyone been successful with using the kitting module to achieve something similiar to this scenario? I am thinking that the assembly would be the parent and the free goods would be the "child" or "component/feature".  For sales order purposes, the customer would only order