The roof top was made by Innovation Campers in Germany.where did you do the roof top ? custom ?

There are a few other ones doing such constructions. Custom Campers for example.
If I had to do it again I would chosse a full rebuild of the back side like this one is:

If you have the opportunity next year, have a visit at the BTT in Germany. A great Toyota Meeting always the 2nd weekend in september. A few guys from Poland always are there.