Great work ... I think a lot of what I didn't know about positioning the trombone slide correctly today is half of what I know. I'm sorry I could not come to your workplace and learn. But I have used these lessons of yours to the best of my ability and have had successful results so far. Thank you for making this video of yours a great help.
The curved piece on the end could have you check 2 measure that from the other end and just using your two drumsticks... Like you showed me.. Put it on the granite slab and then use the drumsticks to check that piece... Because you checked all the other pieces but that one piece that connects both of the tubes the curved piece, you didn't put that one on the granite slab like you did the other ones...