"Arch" wrote: 3. When the headstock end of a long heavy blank held with
tail support is balanced with counterweights adjusted on a steel plate, is
the entire length of the long blank now in balance. (ie. do I need to
balance both ends of a long heavy blank?)
^^^^^^^^^^^^^^
I know this one, so I will answer. The *other* number 3, and the others as
well, will have to come from those with better info.

If you balance a long, unbalanced piece at by adding all the weights at one
end, you achieve "static balance." The piece will stay where you stop it,
and not fall/rotate to lower its center of gravity. However, if the ends
are differently out of balance, you have "dynamic unbalance." The two ends
will try to behave independently of each other when spinning, and you get a
tilting, end-to-end vibration.