Spinning Experiment Calculations

I'm still not finished with preparations for the Experiment test run. I have forgotten to ask the lady running the pottery workshop how much the clay will shrink upon drying and firing, so I'll have to make a wild guess at somewhere between 3 and 10 per cent. Then I have some serious doubts about whether some of the spindle whorls will be workable, since trying to reduce weight while keeping the same Moment of Inertia leads to a thin disc of a whorl... made from ceramic. Used for real-life spinning... where a thread can break. And so can the whorl (unless it breaks when firing first).

Ah, science is fun. I can't wait to break the first few whorls on my next day of fumble-spinning. And should those thin and fragile discs really work... I'll make a bunch more for the experiments. And maybe we can substitute the clay for the big-but-thin whorls with some material with the same density of the fired clay - preferably material that is not as fragile as a 3 mm thin disc of ceramic.