Have you ever drove a 1/2 full fuel tank with no baffles, Picture a long cyl 1/2 full of fuel goin 55 mph and step on the brake, there is quite a large surge from the fuel weight slowing down from 55 pushing on the front of the tank, the larger the dia and length of the tank the harder the push, now fill the tank full so there is a pressure in all directions and step on the brake, the surge is gone but there is a steady pressure from the fuel weight, a tank full of fuel will be harder to stop than an empty one, I would think it be the same on acceleration