Hello , , , thanks for your answers, that makes me feel safe enough to choose this option.
My favorite disadvantage remains, the higher price.
Regarding UP: I still can’t really imagine it, I thought at least the controls and the shower part would be "normally" installed. And the water supply, that comes out from the wall below the edge of the bathtub...? Ok, the connection from the controls to the water supply must probably be UP then. Sorry, but I think it’s the first time in my life that I’m thinking about such things. My goodness, what a nice life I had, everywhere in my parents’ house and in the rental apartments everything was already there, window sills, faucets, sockets... and I never thought about why and where things are installed.