We have to look at the stated "gross weight" and figure out how much fuel you could put in the plane and how many bombs.
Then we have the overload weights or max weights and the B-17 gets absolutely screwy here.
B-17E may have been 40,260 pounds gross, 53,000 pounds maximum.
B-17F may have been 40,437 pounds loaded, 56,500 pounds maximum.
B-17G may have been 55,000 pounds normal loaded, 72,000 pounds maximum.
There may have been in between loads and/or refits/upgrades.
How much was paper upgrades and how much involved new parts?
What were they actually operated at?
Some of the early ones had problems breaking landing gear while taxing on certain typed of air fields and/or were prohibited from doing pivot turns when over a certain weight.
However it does really leave us wondering what the bomb load of B-17 was
B-17G 32,720 pounds empty, no guns, oil crew and with ??? radios ??