Actually, sitting in an uncomfortable position hasn't been a hindrance in my experience. Some of the quickest progress I made when I was learning the jhanas was when I just couldn't find a comfortable seat anywhere and I just had to accept the discomfort. If letting go is your meditation "technique" then it might be worth trying a little masochism and seeing where it gets you.

That said, if it's always painful you probably won't want to keep doing it, so I agree that finding some alternate positions is a good idea. ^^ Daniel is right about standing! I love to stand at my window and watch the soy beans blowing...