Jon A. writes:

No, the myth that an owner could just willy nilly make up a part on
his own.

I don't expect you can make a prop out of adobe and use it, but other
than silly extremes like that, yes, you can make your own parts.

See:

http://www.geocities.com/CapeCanaveral/Hangar/5511/

towards the bottom of the page.

-jav