Hiho,
here is my short description to design formers in Rhino.
I'm using the command: "_Offset" or from menu: "Curve" --> "Offset Curve"
Now select your intersection line.
If you don't want the former right at the end of a part, you need to project a new intersection onto your part first.
Next step is to point to the inside. The "Distance" in the command line gets your preferred paper thickness, or twice if you wanna do joining tabs, too.
(thickness of 120gsm paper is around 0.125 to 0.15mm, 160gsm is around 0.2mm as an example)
If you are designing just a half fuselage, you probably need to trim the former lines to the centerline, this is not needed when using full hull intersections.
Now you got your formers. If you also want longitudinal formers, you have to care for the thicknesses of the formers, which could be skipped mostly on "intersection former only" designs.
My trimmed and mirrored formers next to the original lines.
In the same manner you could add tabs to your unrolled parts, by offsetting 2 lines.
