I honestly don't get this. The Mk1 and Mk2 (fuel tanks specifically) carry the same amount of fuel. However, The Mk1 parts are lighter for the same thing. Yes, I get that the Mk2 parts have lifting body, but if you look at the end sides of the Mk2 tanks, you can see what looks like a hollow space. Anybody think that that should have some fuel in it? -SPAddict