I do have one suggestion you might consider when you make another turning this tall. I would make it in two halves with the bottom half ending at the widest point or in this case, just above the feature ring. Make the other half from the top down, but add a sacrificial ring above the top ring. This will let you turn the inside of the halves when it is easy instead of hard. I'm sorry I'm telling this to you now, but I missed that comment of your earlier email.
I completely turn and sand the insides of the halves when I do this and just use a caliper to make sure the insides where they will be very close. When you glue them together, you will only have to work on the transition area and since nobody's hands can reach it, it isn't very critical. I leave the final outside turning for after the halves are glued together. On my lathe, I have an adapter that lets me mount a faceplate on the live center so that I can turn the glued vessel at high speed with no wobble.