Nice tool holder! I would expect chatter city though on a tool that size. Maybe a bit Axelson or Lodge&Shipley would be fine with it, but anything less than 6 or 7000lbs is going to struggle. The problem with chatter, especially on a form tool, is that it's self reinforcing. The peaks push the tool away which then springs back and takes a nibble out of the valley. The only way to deal with that is to either very lightly shave the peaks off by rotating the work with no feed or by pushing under the chatter marks (= difficult on less than monstrous lathe).
If I were going to make something similar I would start how you did, with the stepped cut. But then I'd work out the cuts in Excel (basic trig), swap to a round nose tool, say 1/8" radius and repeat. If your steps are small, say 5 thou, you'd get a near smooth radius. Then a bit of sand paper wrapped round a stick to finish off the smoothing. I made the mortar part of a mortar and pestle for my wife out of stainless this way. It was a fairly miserable process on a small 6" lathe (mortar was ~2-1/2" diameter) but it came out really well.
Not saying the way you did it isn't a good option, you clearly got it done and it looks good, but this would be another approach to put in your pocket for whenever you might need it.
