Do you mean moving the trigger (the blue rod that locks the chain in place) towards the end of the launch? If so, I thought I already made that clear. (In the video the trigger is also one red rod size towards the end of the launch, which gives the rubber band more space to stretch).
Oh, no, I don't mean moving anything, only making the long black rod in the tutorial able to be rotated from the train hitting it by adding onto it. Like the black rod Gumps' talking about:
The train doesn't trigger the launch in this tutorial. You see the black rod sticking out to the side? Rotate this rod and the trigger will let go of the chain.