Most body parts cannot be saved you inlarge them beyond what is allowed by the game code. This does not mean you can have a good laugh in the creator and see them run around. For this just look at the cheat sheet for the part you want to make HUGE. Then enlarge the part to its max and search for the value that is listed on the cheat sheet as the Maximum value. Then shrink the part by clicking two the down arrow two times on your keyboard and searching for the second value listed in the cheat sheet. Now change that value to whatever you want, but keep in mind that if its too big, you wont see it.

Here is a clip on how to do this: youtube clip         

Here is a crazy one I just thought of: youtube clip