cut the wings just past the engines and replace control surfaces, you have too much drag. lose the intakes since they dont do anything yet. add drag. I suggest restarting from your Fat Man Turbo and adding engines along the aircraft body instead of on the wings. This way the wings will only have to worry about the lift instead of weight. Either way, your aircraft seems to me to be on the lifty side of things. try even less engines AND less lift surface, use boosters on takeoff if necessary.