The first plan was to make a liftable roof so we could stand in the back of the car. But we also wanted some storage boxes on the roof. So why the need of a liftable roof if the vehicle will be higher anyway? So the final plan was to make a roof extension with boxes on the side you can only get into from inside the vehicle.

The aluminium plates from the collapsible crosses on the outside were used to make the roof. The material for the boxes was new. The whole thing is assembled with pop rivets and kit.
The section of the roof I cut out was exactly the same dimensions as the alu plate from the cross which was on the roof. This way I could keep the original roof hatch.
On the inside I glued a wooden framework and insulation material before finishing.