The wall tells me your from germany too, so you have about 5-6 weeks of flower, topping outside is imo not necessary. The sunlight penetrates deep into your plant and doesnt get weaker by distance because its 10000000000Meters away anyway, a meter more or so doesnt matter. So you dont need a flat canopy. I wouldnt top her at all, just defoliate, so your whole plant get light. Cut big leaves that shadow other leaves in the middle of the day. Also dont lollipop, the sun hits your plant with a good angle to reach even the lowest parts.