Each new piece of metal added to the fuselage makes the geometry shift. Even a perfect fit will cause the fuselage to shift as it is "snapped" into place. I keep the plumb bobs set all the time. They are right there in front of me so I can see when thi
Blocks holding the longerons in place.
Adjustable clamps that criss-cross the bay.
Keep that plumb bob on the centerline. Check often.
