MacOS and multiple (concurrent) Vagrant boxes

Are you running more than one Vagrant box concurrently, forcing you to resort to port numbers for correct working?

I am, and it's been annoying me for quite a while. Every of my sites has its own specific VirtualBox VM. Sometimes I might work on more than one at a given time (eg 2 sites communicating with each other via an API) so keeping them on the default ports and then only using 1 at a time wasn't a real solution.

So I decided to spend some time on the matter and see what I could trump up.
As it turns out... a lot!