Yes, this is possible.

I have driven for over an hour with the tailgate open and the hatch closed. To do this use what we call in Australia an 'Octopus Strap'. This is an elastic strap with a hook on each end. One hook goes into the central latch on the hatch - push it in so that the latch locks around it - that way the car thinks the hatch is closed. You release it by pressing the boot (hatch) unlock button on the remote or centre console.

The other end of the 'octopus strap' goes to one of the luggage hook / tie down points in the back of the car to keep the hatch closed.

The only issue you will have is number plate not visible (may be a problem with local law enforcement???) and you will get exhaust fumes into the cabin so you may need to keep your window down a bit to get some fresh air!

Works great for long loads!