Change speed of a running iTween

I have a running iTween and I want to change the duration on the fly (i.e. without restarting the Tween). Getting the iTweenComponent and reducing the time value produces very strange results and seems to destroy the path.
Does anyone know, how to do this?

I don’t know how to do this with iTween but if I get you correctly that’s what is shown in this HOTween example here (changing parameters while playing)