Passing VMWare Customisation Spec in Foreman

I am trying to provision hosts using Foreman on VMWare using Templates and
pass customisation spec. I have managed to register the Template (as an
Image) in the VMware compute resource although cannot find a way to pass
customisation spec while provisioning. Can someone please share their views
of how they managed to achieve this or any other alternative workflow that
you would have used to achieve this?

Details of the environment:
Foreman v1.6
VMware v5.5
Provisioning RedHat 6.5 x86_64 guests on the VMWare data center.

Thanks & regards