My NACRA Square boat has a boom. Came from the factory that way.

Sheet tension against my boom, boom pushes the mast to rotate, so all I have to have is a rotation limiter.

Note that with a boom, I do not have a big triangular bit at the front of the mast which also is known as a rotation INDUCER or over-rotator.

1980s and early 90s NACRA Squares carried a boom, later NACRA Squares were boomless, custom and other builds vary. Box rule and all that.