The first stage of stitching a 220 megapixel stereoscopic panorama from 2 rows of 12 views taken with a 16mm fisheye lens.  In PTGui 12 Pro, apply centered sector masks about 90 degrees wide, generate control points, align and stitch, giving this monocular panorama.  The left and right eye views are then stitched by substituting off-center sector masks, without changing the alignment.