Sorry Scott, and this is solely a matter of personal aesthetics, but I don't care for the look of the butt ends of cut hackle as a collar. If someone wants or needs to use 'oversize' fibers for a collar then simply cut them from the stem, measure to the length you wish to use, grasp them at the tie in point, wind the thread and then maneuver the fibers around the shank as the thread is tightened. Even if a 'split thread' method is used, the butts of the feather should be cut as close to the thread as possible.
But just to let you know, I appreciate all of your SBSs. Always well done and described.