If the train has a velocity, there will be two different transit times. How do you reckon that with the fact that you are midway between the two clocks, since light travel time defines distance? So you took a piece of string and ran it from one end of the train to the other, cut it to the exact length, and then folded it in half so the ends lined up and cut it at the fold, to have two equal pieces of string. You take one string and start it at one end, and sit at the other end of the string, and whala, you are at the midpoint of the length of the train. If the transit time of light takes a different amount of time to go from the middle to each end, how do you justify your midpoint position, since light travel time defines distance?