There were two types of set up for the business coupes in 1929. The 28 & early 29 models had no window and used all the same stuff as the sport coupe except there was no landau bars or mounts for them. The oval window set up came along later in the 29 model year and has a frame that supports the rear bow on the sides and also holds the oval window. This frame attaches directly to the wood main bow & down to the rear tack strip but it has to hold the whole rear bow on the sides so it's a bit beefier than the ones for the sport coups and earlier business coupes with no oval window. You can see photos of it in this link.
http://geraldandsonsrestorations.com...usiness-coupe/