Jack I am not sure as to that you are referring to in regards to the "Tee" at the top of the chamber but mine is a RM2201 and based on photos posted by OP it looks to be very similar.
Yup a detector is a must have as well. As you say you cant smell the really bad stuff but I have to wonder based on the original post if perhaps not only is the back not sealed correctly if the burner isnt burning cleanly either - if I was able to smell propane
when any of the trailers appliances are running I would be worried its not burning the fuel correctly either - dirty burner perhaps? As said it would be worth having it checked by a certified gas tech.