Yes you can get the smaller drum for 52's. Some had 7" in newer big machines that had four strand chains. They had some feeding issues and put 8" back in and claimed that fixed their problem. I would insist it was something else if they had better luck with 8". One is maybe they tensioned up chain proper after installing the 8" drum, two this brought the chain closer to floor if they did nothing with their drum stops, three is maybe didn't provide such a large clearance under drum when it floated all the way up if they hadn't changed the stops, four is the four strand in larger machine have slats to close together on the center runs of chain. If it could of been to much clearance under the drum when floated all the way up they could of shimmed top pad down. If they had drum stops set so there was excess clearance from floor to chain when empty they could of had stalling in their condition and could of repaired that by letting the drum down. I find recommendation advertising to have drum high off the floor or in corn position for small grains. This will not work in our tough to convey spring wheat or barley straw. I like the 7". The 7" with W rings does have the chain running at a fairly similar diameter as the 8" without the W rings. If you have a chain that is new enough so slat is flat accross the attaching links and you have a drum with W rings you can add the 1" X 1" angle irons to drum to act as a beater. This keeps the straw knocked down and going under the chain.