Hello Ace,
The shroud extension system is just like any other "system". Either get all of it or don't get any of it. This includes a captive mast step base. This base also is a safety feature. It keeps the bottom of the mast on the ball while raising and lowering the mast. The mast can't slip off the ball or out of the pivot and fly up and hit your crew person in the face in the midst of raising or lowering the mast. I have seen this happen on some systems.
Bill