It should end up just short of the bottom of the jacket. Holding the model as illustrated, use thumb to roll out paper to form an arm. Repeat to form the arm on the other side. Mountain fold the shoulders behind. Thin out the sides of the pants using mountain folds.
Mountain fold the inseam of the pants.
The easiest way to do this is to pinch the folds through all layers, then fold behind just the top layer. The suit is ready. To make it stand up, turn the model over. Holding down the back of the jacket with one hand, slide out paper from underneath and make the flap stick straight out. Repeat step 15 on the other side.