Suggestion: place the panel on top (ALL flavors)
Reasoning: at least with virt-manager, you usually don’t put the VMs in full-screen in order to easily switch between different VMs and/or Host programs.
With the current settings you end up with something like this:
i.e. you never see the panel (hidden below) and you have to enable full-screen again to do anything useful inside the VM.
With the panel placed on top, you can still access it and manage your opened applications in the VM without having the need to enable full-screen, while still keeping quick access to your Host applications:
Much more practical! Also looks better and more functional IMHO. Top panel is actually default behavior for many XFCE distros (debian with XFCE, Xubuntu…).