How much time do you have to do the shot? You problably are using a fisheye at the moment. What is the next focal length you have? 24 mm? Do a test with that length first. 24 mm would mean making at least one photo every 24 degrees horizontal for a non FF camera. Make shots at +90, +65, +40, +15,-10, -35, -70, -90 vertically Use import wizard to import a pattern of 8 rows and 24 photos. Of course you can decide to do only the rows around o degrees vertically. You likely need a very strong computer to get this done. If you don't have such machine feel free to dropbox the photos to me and I will give it a try.
Regards, Hans Keesom I stitch and render for other photographers. Price: 25 euro or less, no cure no pay. If you want to concentrate on your business let me do the stitching for you. Free TB of Dropbox space when you have more then 250 euro business a year.