Here's an idea I'm working on now while I am updating the expansions to FDD.
As long as the Fuel Transfer pump is operating the first leak on two separate tanks are no effect. The second leak on one tank is Treated as a Leak on a third thank (Player’s choice). The first and second tanks will be considered empty from this point.
When the third tank is empty, the fourth tank is Treated as a Leak. If the third tank leaks before a second leak on another tank see 1st leak on main/outboard tank.
Should the fourth tank leak before the third tank is empty see first leak on main/outboard tank and keep track of how much fuel remains in each tank.
When the third tank is empty, fuel from the fourth tank supplies both engines. Divide the remaining fuel turns by 2 rounded up.