All the info about loading E2 talks about using flash or a USB stick.

Is it possible to share the internal disk between a DGS based install and a E2 USB download on it or will the DGS based image always reformat the internal drive on boot?

The reason is I want to install both DGS based and E2, or even multiple E2 images to play with, but still be able to go back to a DGS based one for the rest of the family while the E2 releases mature.