I cant really comment on the validity of growing the segment vs placing a cylinder around the segment as I dont know the project.
Looks like there are some great new features in Segment Statistics. You could find the centroid of the segment, place a cylinder model at the centroid and then align it with the principal axes of the segment (also found with segment statistics).
You could probably write a script which calls the logic of segment statistics to find centroid and principal axes and then places a vtk cylinder at the centroid and aligns it using a transform or perhaps you can specify angle on placement from the cration options for a vtk cylinder?