Hi guys. I'm trying to model fuel tank with 3 time more fuel then regular, and 3x bigger. Idea is to make a bigger tank, but that will correspond to 3 regular tanks. Basically, I have make it 3x heavier, 3x more fuel and so on. I will make one 2x size, 4x size and 5x size. I wan't them to act same as equal number of regular tanks, so maybe in that way I will be able to remove some lag (less objects to deal with) when you build big ship, and still maintain same performance as regular parts. But I have couple problems... First one is drag parameters... I can't set them to correct value to make my big tank (as 3 regular) to act in same way as 3 regular. Here are my current parameters: By logic and test, I have come to conclusion that drag parameters are problem... I can't set then in right values to make my tank act same as 3 regular. With bigger values (as are current) thruster with my tanks speeds up at start, and then starts to lag behind... With lower values and same values as regular tank, it lags at start, and then it speeds up... Does anybody know how those parameters act when couple same parts are stack up? Does engine calculates less drag for lower parts, or they produce all same drag? If is first case (less for lower parts) then drag of my tank should not be 3x bigger, but less then that, but I can't figure out what value to put. I have attached my full config file.