DETROIT/NEW YORK (Reuters) – Auto analysts are skeptical that Sergio Marchionne, the hyperbolic chief executive of Fiat Chrysler Automobiles (FCHA.MI)(FCAU.N), can meet his most ambitious goal: to nearly double Jeep’s global sales over the next four years. Marchionne reiterated his aggressive target for boosting Jeep’s annual volume to 1.9 million, while pacing the floor of the New York Stock Exchange on Monday during the newly merged company’s first day of trading.