Yes, they do work but are a little clumsy and you have to change it every time you use someone elses gun, but it`s fine while you make up your mind if you want to do it or not. Ha! a waste of money though if you don`t.
If you do decide to give it a go then keep looking in as many shops as you can until you find a gun that fits. You may find one that has been extended for someone else or has a very large butt pad. They are out there, so keep looking.
I would however advise a lesson with a good coach, he will help you hold and mount the gun better so you have less recoil and can advise you on anything else.