I am still challenged by non leveled panoramas. I levle the NN5L bubble in the center of the small circle, but I still end up with panoramas where the view is at an angle. I purchased a hotshoe bubble and have used it for the zenith and nadir shots. I have an EZ leveler, but I do not use it anymore because it tends to unscrew when I carry the tripod around with the pano head attached when I am taking multiple panoramas.
I have used the leveler in autopano and ptgui, which often helps, but some times, it causes other problems. The list also is from right to left which is the opposite of what I would expect if it was due to flex in the upper arm. Maybe it is my center pole on my manfrotto 3130 tripod?
Is leveling in your stitcher and standard step in your stitching, or is reserved for occasions when this is a problem?
Do you use a hotshoe bubble just for the zenith and nadir shots?
My stitching has become simpler and faster since I found out about the cylinder on the sigma fisheye and I have reduced the number of shots and rows that are required.