So..the progress of today, the 3d engine has been fitted, pointing slightly upwards, wchich allowed me to set the front engines more upward too.
Then the soldering began..about 2 hours
Never had so many cables in one model! Anyway, everything is finished now. The controll layout:
Throttle = all 3 engines
Yaw = rudder
pitch = Elevons up&down
roll = Elevons differential