Building HVMs Using Packer/Vagrant

Hey, there is a large community around Packer/Vagrant and there is even a large repository of VirtualBox images available at vagrantup.com. VagrantUp stores VirtualBox images as .box files but in the Qubes guide, it says you can make HVMs from .ova files (here Standalones and HVMs | Qubes OS).

I’m just wondering – what would be the best way of leveraging VagrantUp VirtualBox .box files to create HVMs? And are there any special optimizations that would improve the performance of the HVM?