When is a Cop a Whorl?

I set up one of my Viking Oseberg-style spindle sticks with a v-shaped Nok on top so it would spin with a pottery whorl on the bottom.  I dressed my Oseberg-style Hand Distaff with drum carded batts of brown anonymous fleece. To see my spindles and distaves in action, go to the missingspindle YouTube channel here.  I spun until the spindle got too heavy to revolve well, and removed the spindle whorl.  I continued to spin, using the yarn cop as the whorl until, once again, the spindle got too heavy to revolve well, and my fingers/thumb joints were complaining.

Then I rolled a ball off gradually, photographing as I went.   I am pleased with the result.  Once the spindle got to 2 ounces as I was spinning, it was definitely time to remove the whorl.  Soon, I'm going to insert a home-made video of this spindle and a hand distaff in action.  Not made with a fabulous camera like the YouTubes above, but I hope useful.  Below are the pixs:

The spindle with 3 ounce cop, and no whorl. 

Then I kept rolling to 1 ounce -whorl in place

2 ounces (whorl should be in place 

then 3 ounces (whorl should be in place)