Choice of wood: Use closed grain as opposed to open grained ring porous type. You can use green or air/kiln dried wood. If the pith is present, offset the pith from stem location. The better the finish texture and wood uniformity, the smoother and better finger feel.
Chucking: Use spigot or 3 jaw type chucks. Try to use the full back to front depth for better holding power. The long overhang from the headstock makes this attribute very critical to the project. Shallow jawed Nova/Oneway chucks have holding limits. A tenon cut on the blank aids with holding. Accept the fact that some of the wood length must be dedicated to holding the work.
Turning Speed: Run at the upper end, medium to fast versus the lower end slow speeds. This helps eliminate an oval stem caused by tool pressure.
Steady Rest/Support: Expect to use a steady rest, back stop, or another person helping to negate the vibration and chatter while working at the cup. The long overhang and the amount of material being removed while hollowing the end grain can caused vibration problems. Another person using an auxiliary piece of wood in support like a backstop can help to minimize this.
Work In Process Finishing: Final sand and apply sealer to cup before moving down the stem towards the base. The projecting end is not fragile at this stage.
Tail Stock Support: Timeliness is critical at this point. Bring the tail stock up and loosely tension it before completing the outside of the cup or starting on the stem. Do not adjust the tension once it has been set. This will remain as set until completion.
Turning Discipline: Try to maintain a continuous turning effort to completion, hopefully in the same turning session. The uniformity of tool work and rhythm of the turner can yield a very uniform stem without the need for calipers.
Tool Work: You can use a side-cutting gouge with the bevel rubbing. For the stem, you can cut either direction and use a peeling/paring cut at the critical dimensions.
Photos by Frank Stanko