It's a property you need to set as part of CloneVM_Task - http://www.vmware.com/support/developer/vc-sdk/visdk400pubs/ReferenceGuide/vim.vm.CloneSpec.html
Within the VirtualMachineRelocateSpec, you'll set the diskMoveType as createNewChildDiskBacking as you've referenced from the VMware WP on Linked Clones with vSphere 4.0 API
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William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at:
VMware Code Central - Scripts/Sample code for Developers and Administrators
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