Design it better??? There are a few aircraft that the pilot need to keep track of the fuel level in the craft's several tanks, just to make sure the craft will fly as the designers wanted... If i don't remember wrongly P51, f190 had a to be manually adjusted so the CoM wouldn't move to a strange or even dangerous position..... and my belive is that both of them were as well design as they could be.... Pd-> Even the B17 need those adjustments to fly properly....