I had already set the period to be dependent on the platform.VectorX when the grappling is shot. The thing is that the period doesn't affect how far/big is the swing, it only affects how quickly a full cycle (4 x magnitude) is done.
How I was trying to solve the problem by finding how much was the angle from the green to the red in relation to the total of the full cycle. And add that to the 0.25 (a 1/4 of the cycle). But I must not have implemented it correctly because it just doesn’t work.