Perhaps one of the best I've seen is placing the feet together and swinging easy. If your balance is off it will cause you to feel like you're falling off to one side and you won't be able to remain with your feet stationary. This might help with the lean forward. One you find you can swing this way then take up that stance then just sread the feet to a comfortable distance and try your normal swing. You might also want to video that repeatedly to see if you change when you go back to your normal swing.