Hmmm, yeah - my first thought on this back when I started was to begin with the base tube and then laminate layers of sheet onto it to get the successive steps. The 1" outer diameter should be right - that's based on pretty clear dimensions scaled to the Vader wing (unless my outer-most ring is too thick, I suppose, but it matches the photos.)
The assumption that the body is based on 2" tubes goes way back to the very earliest discussion of the topic - I've never personally checked those figures against reference materials, perhaps I'll sanity-check the 2" tubes against some of the kit parts and see if they'll really fit together as expected.
BTW, I think the conclusion drawn earlier in this thread was that 1/2" wasn't big enough for the cross-support, and that 5/8" is more what's been typically used. That again requires ordering plastruct, or using brass tube (my Ace carries 5/8 in brass and I've got a few on hand.)
If the body is actually a size smaller than it would make sense to go down to 1/2" for the wing support as well - again, I'll experiment a bit this weekend and see what conclusion I draw.
I've got a pair of railgun frames cut down for the top and bottom of the pilot's fuselage and I've got a 2" dome cut for the front window, it should be possible to determine if the kit parts fit correctly on the 2" diameter or not (although a few people on the thread have built bombers, I doubt that this oversight would really have stood this long.)
I can cut down a pair of the railgun frames for the front and back of the wing-strut, too, and they'll either fit a 1/2" piece of tube or not, it should be pretty clear by then what the sizes need to be.
...Hmm, and I wonder, 1/16 wall thickness actually seems right - if we need to get from 1" to 5/8", and there are three steps if I'm remembering correctly, then we need to lose a total of 3/8" in total diameter, and a 1/16" wall thickness will shed 1/8" per step (2 x 1/16) which actually seems to add up right...? Again, bears photo checking It'll be a productive weekend...