I've quit running Windows on my Macbook Air (my main use for Parallels). I've since moved to using VirtualBox because the Linux support (I mainly use Kali in a VM) is vastly superior. Whenever I install Parallels Tools inside any modern (Ubuntu 16.04, Kali) Linux VM, it completely breaks. Seeing that Parallels 12 doesn't resolve this helped me make up my mind to not pay for the upgrade when a free tool is superior.