The correct point of rotation for this type of panorama is the entrance pupil, not one of the nodal points. It is fairly easy to estimate the position of the entrance pupil: stop the lens down enough so that you can see the iris, then estimate where the iris appears to be (not where it actually is) when you look into the front of the lens. I find that it helps to put my finger on the lens barrel and move it into the plane of the entrance pupil.
If you do get data for the lens, use the location of the entrance pupil, not of the front (first) nodal point.
Best,
Helen