.. the stem fully around the carbon steerer , then having the HS preload adjustment gap,
half of the spacer above.. it's thickness, would seem the prudent plan.
I could have sworn I read some manufacturer blame a steerer explosion
because of lack of spacers under the stem increasing stresses.
well this is when you foot note that reference ,for others to read,
and make their interpretation..
simple lower leverage would suggest shorter the better ..
taller a steel steerer has benefits. just minimum weight is not paramount.