A straight cylinder bore 20 gauge would be borderline worthless IMO and it is hard to believe that someone would think that it was a good idea to bob a 24 DL barrel like that. My own 24 DL .22 WRM and 20 gauge puts slugs within about 2 inches of each other at 50 yards. We can use rifles state wide here for deer, so I don't see myself ever using that 24 for slugs, but it was a good thing to try at the range one day. In your case I'd start over and sell that short one.
