I use the hot water treatment for Airfix U.S. Cavalry to get him to stay on their horses. I dip the trooper in boiling water up to his waist. I then hold for only 4 to 5 seconds, then pull out and squeeze legs, then hold squeezed figure under cold water.
Warning: Small pieces such as Airfix swords, sheaths, etc. will actually shrink-up under boiling water and will not go back to original shape. So test an extra figure first.