Scale tension and scale stiffness is tough to achieve. You would need carbon spars for these thin wings to be stiff enough. The real airplanes have the wires tensioned in a specific order or they will deform the full scale. Pre stretching the cables is smart. I spent a day chasing cable tension on some flight controls of a real plane because they were not pre stretched. The little turnbuckles will not have enough to take up a bunch of slack.