Karasuaki
You may want to try to be on top. This way you can choose how deep he goes in. You are controlling what is happening.
By the way, this isn't true. It would only be true if he stayed completly still. But since men can (and often do) push upwards with their hips, it's not true.
I find missionary to be a better position because it's quite easy to position your legs in such a way that he can't get too far in. My fiance is rather large and he knows this, but he does get into it sometimes and it can hurt. But simply being in a position that prevents too much penetration can really help.