vagrant-parallels: "hostonly" instead of "shared" for Adapter 0

Dear Community,
As I understood whatever happens, vagrant creates an adapter 0 for its internal usage. By default it will be a SHARED connection:

Code:

==> default: Preparing network interfaces based on configuration...
    default: Adapter 0: shared
    default: Adapter 1: bridged

(adapter 1/bridge goes to a closed LAN.)
It is OK, I can live with that.
But I would like to have this as a HOST ONLY interface.
I poked around config.rb @ https://github.com/Parallels/vagrant-parallels/tree/master/lib/vagrant-parallels
I think line nr 31 is responsible for this.

Code:

 network_adapter(0, :shared)

I tried to change the behavior without luck. I get this if I set it to hostonly

Code:

Network settings specified in your Vagrantfile are invalid:

Network settings: {:auto_config=>true, :mac=>nil, :name=>nil, :nic_type=>nil, :type=>:static}
Error: address family must be specified

My question is: Is it possible to somehow tell vagrant/vagrant-parallels to create the adapter 0 as a HOST ONLY interface? How could I isolate the guest if I cant change this?

Thanks.