Don't the tanks always equalize when the engine is running? I thought that was how they work anyhow. I'm pretty sure my tanks keep about the same level judging by when I'm filling up anyhow. I don't think there is a crossover line at the low point on my tanks though. I think there is some way they circulate the fuel between the two to keep them equal.
'03 Freightliner FL112, 295" wheel base, with '03 United Specialties 26' living quarters, single screw, Cat C12 430 h/p 1650 torque, Eaton 10speed , 3.42 rear axle ratio