If you don't get a response in this thread then I'd try PMing the used Bobdadrumma. he hotrodded a beautiful vintage Gretsch with a 20" BD and added a few Atlas mount. I'm sure he ran into a similar issue with his kit.
If anyone owns a 14x24 with the atlas brackets can you tell me the best brand and size bag. I'm thinking a 26" since the drum with the brackets it measures 29", a 26" Protection Racket case measures 29 1/2" inside. I sort of answered my own question but has anyone had success with a smaller bag.