Sounds like he got a concave for a later machine. The earlier machines had the canves and adjustable plate like he described. Some earlier machines have been updated to accept the concave he got. The trap door latches on a stationary crossmember on the later machines or the updated earlier machines. Trap door latches on that adjustable plate that he describes on the earlier machines. I have a feeling that wrong concave got ordered which wouldn't be loewens fault. I use mostly all OEM for the fit is usually perfect. I have had very little problem with the fit of loewen stuff but no one is perfect. They have been quick to remedy a problem. loewen has been very nice to work with when we needed something special like extended cylinder bars, seperator grate covers, shock kits, ect. ect. I guess that is the main time I use them is for the special stuff and or normal stuff where they have added a refinement to make it better than OEM. Just remember if you have problem with fit or finish on something you should spend as much time expressing problem to builder as you do complaining and you will likely both benifit. Good luck with your project.