Great result Stephen. You have handled the inevitable distortion to the top of the frame well. It is harder to do Milkyway bow images when the central bulge is rising in the east as the area around crux is so high in the sky. Much easier when the bulge is about 45 degrees above the horizon in the west. I always say it is better to have lots of overlap than not enough but 58 images is probably a little extreme
But hey, if your computer and stitching program can handle it then there is nothing wrong with it at all. By using so many images you are negating any illumination or coma issues towards the edges of the frames by using only the very middle of the images. At 11mm on your x1.6 crop camera you are getting a horizontal field of view of about 91 degrees and vertical of about 69 degrees, so based on this images field of view I would probably do about 16 images (2 rows of 8). Double that if you want to be ultra safe. Any more is probably not worth the effort. You are not gaining any more resolution unless you go for a bigger focal length lens like a 24, 35 or 50mm. You might need 50+ images then. I recently helped a friend stitch together a pano he had done at 50mm focal length that contained nearly 100 images. My computer hated me that day.