Personally, I want the hold down adjusted so that it is just tight enough to
not allow the stock to raise on the upstroke, but not so tight that I can't
easily move the stock laterally for the next plunge.

That was my goal, but I couldn't seem to make it work very well.
Granted I didn't fiddle with it very much, but the hold-down was
nowhere close to parallel with the table. I'd hold it down against
the workpiece, but as I tightened the holddown bolt, it would torque
the clamp face up at an angle. This left only the very back of the
holddown (nearest the fence) actually touching the wood, which allowed
the workpiece to lift up at an angle as I retracted the chisel.
Any advice for squaring the holddown, or for keeping it parallel as I
tighten it?
Thanks for the input,
Andy