The maintenance of an Overweight rating by JP Morgan suggests a positive outlook on Constellium's stock, indicating confidence in its fundamentals or growth prospects. However, the reduction in the price target, albeit slight, could reflect a minor adjustment in expectations regarding the company's future performance. This adjustment is likely based on JP Morgan's analysis of market conditions, potential challenges, or revised earnings forecasts for Constellium. The impact on the stock price in the short term could be neutral as the positive sentiment from maintaining an Overweight rating may balance out the slight negative sentiment from lowering the price target.