NavMesh defines the players limitations of travel by the creation of a collision mesh. NavMesh sits exact or slightly on top/next to existing asset geometry, you do not want too much space between or the avatar/pod will be hovering or hitting walls to early or late when moving around in the scene. Keep as realistic as possible for gameplay.

MAYA : Notes

Tip : Duplicate existing geometry of asset then begin to cut, sew, and collapse geometry to downsize the amount of tri count.