Thank you Mr. Smith!!
Here is a much improved train of 6 hoppers and a caboose doing a leisurely 20 smph. The caboose and four hoppers got zip ties. One hopper is an early mth tinplate issue that didn’t have the uncoupled devices and another is a Lionel prewar celebration piece from the late 80’s that didn’t have that feature either.
I am still getting a little slipping below 16 smph but the difference is huge! Thanks again