Upper-story setbacks. The number of permitted stories in the DT, DG and DB Zones shall be three stories. The addition of a fourth story of any building and/or a building in excess of 40 feet in a DG and DB Zones or 35 feet in the DT Zone (up to 45 feet in the DB and DG zones or 40 feet in the DT Zone) may be permitted only at the discretion of the Board of Trustees as part of the site plan review application and only after a reasoned judgment setting forth the public benefits of the development which would warrant the Board of Trustees granting approval of a fourth story and an increase in height above 40 feet or 35 feet as the case may be. In determining the appropriateness of the fourth story and an increase in height above 40 feet in the DB or DG Zones or 35 feet in the DT Zone, the Board of Trustees shall take into consideration the recommendations of the Planning Board and the AHRB in considering impacts, including but not limited to viewsheds, solar access to the streetscape and surrounding buildings, use and enjoyment of the Old Croton Aqueduct (OCA) and consistency with the character of the individual building and surrounding buildings. Based on a review of potential impacts cited above, a fourth story and/or an increase in height above 35 feet or 40 feet, if approved, may be required to recede from the front facade, either within a sloping roof form or as a setback volume and the applicant must use available techniques to minimize the visual impact of any such fourth story or increased height. In addition, in the downtown districts, the liveable floor area of the fourth story, if permitted, shall not comprise more than 50% of the total floor area of the story below.