Normally only their upper body is seen. That is not adult movies.
The best example for a body dounble is in Amazons. The blonde woman is really whipped. you can see light blue marks. Her name does not appear in the cast and she is a very bad acter when she makes the mistake which brings her to the whipping post.
Standard parts of actor/model agreement ( incl. ours).
5. Dubbing: Producer shall have the right to cut, edit, add to, subtract from, arrange, rearrange, shorten and revise the content in any manner Purchaser may, in its sole discretion, determine. Producer shall have the right to "dub" any performances attributed, or to be attributed, to the character portrayed by Artist, and may use Artist's pseudonym, likeness, voice or other sound effects in connection therewith; provided that if Artist completes all of the services required of Artist hereunder.
6. Doubling: Producer shall have the right to "double" any performance attributed, or to be attributed, to the character portrayed by Artist.
