Thanks for the reply...
Alas, no slots, just a smooth plastic end piece, which already appears to have a couple of micro cracks in it (!) not even caused by me, I'm afraid if I apply pressure the piece may shatter. I could maybe replace with a metal end bolt & threading the end of shaft with a tap wrench if not already threaded, or strengthening plastic by filling in cracks with krazy glue or epoxy, etc.
It would seem preferable if the red ball end could just unscrew. I'm guessing these aren't made that way for safety & to make it harder for kids to break. I could hacksaw it off then drill out & thread the hole & shaft, but this is a lot of work & would shorten the shaft (not a big deal). I would be more concerned about bending or scratching up the shaft (I can hold it in a vice sandwiched between wood shims or newspaper to protect it).
Would prefer to take it apart non-invasively if there is a trick to it...
Thanks again....