A method for production of synthetic diesel and naphtha from a hydrocracker includes hydrocracking a synthetic heavy hydrocarbon feed comprising an a value to form a diesel and a naphtha; selecting a desired diesel-to-naphtha ratio; calculating, based on the feed a and the desired diesel-to-naphtha ratio, a target molar ratio of hydrocarbons exiting to hydrocarbons entering the hydrocracker; and adjusting at least one hydrocracking conversion promoting condition to achieve said target molar ratio. The present invention further relates to a method for adjusting the overall production of a syngas-to-synthetic hydrocarbons plant in response to market conditions, comprising adjusting at least one hydrocracking conversion promoting condition and/or at least one conversion promoting condition within a Fischer-Tropsch reactor so as to maintain the overall diesel-to-naphtha ratio or to maintain a diesel production rate within a predetermined range of a desired value.