I suspect that what is going to be done, is go with a constant section tube, with enough milling to fit the attach fittings. At 25 feet in length, about the only way you can easily taper the inner profile, is using a custom extrusion press and a set of closed dies. You are probably talking well into 7 figures to create the dies and the press. Going with a constant profile is way less expensive, but at the cost of a slight increase in weight. The weight increase isn't really a factor, as all of the a/c are operated well below combat weights.
I'd be willing to be Ray Moore is deeply involved in the project, as he's already built a number of both fuselage and bomb bay trusses for various B-17 restorations as well has his new construction one.