hoopsnake + kangaroo, using a moving point to bend a curve

I am writing some structure that will change to accommodate the environment. This is my first try. The yellow arc is the initial setting. The green dot going up will form spring with the closet 5 points on the arc and hence change the form of the arc.

Sometime the kangaroo goes red after the first iteration. It will work again if I turn it from false to true and then back to false. 

Because next step i would like to have a mutual effect. ( the direction of green dot is affected by the curve). Could I turn on and off some forces during the simulation without refreshing the kangaroo component?

thanks