My thought is (1) calculate the most efficent fuel useage for that drive and use it for all ships using that drive, or (2) calculate the fuel consumation for each size hull and then invert those numbers. In the specific example given, the 200 tn hull uses 10 tns of fuel, 201 to 400 uses 20 tns, and 401 to 800 uses 40 tns per 4 weeks of operation.
PS. boomslang, your linked site was down when I tried, so I will check it later.
PS. boomslang, your linked site was down when I tried, so I will check it later.