Not possible to choose Multiple GUI sessions on live install

Hi,

Has somebody tried several graphical session environments installed in the same distro?

My personalized distro (http://XJubuntab.xjesus.net) has xubuntu-desktop + ubuntu-desktop and also testing unity8-Mir-desktop but when I select any of them from the live install session, I only log into the XFCE session...

Can somebody give me some advice to correct this? Is this something in my distro config or PinguyBuilder not supporting this?

Thanks for your help!