I have tried this experiment many times using a few different 8K stones, (Naniwa Snow White, Fuji 8K, Shapton Glass 8K) to name a few.I would be curious about what people think about going from 12k to hard Ark.
I ask because I remember reading a thread about people getting better results going from 8k to hard Ark, but this is from memory.
Then I tried Shapton Glass 10K & 16K, Naniwa Pro 10K, 12K SS and a few naturals like Coticules, J-Nats & Thuri's.
For me the Nani 12K SS gives very good results if I'm jumping off a synth to the Ark as a finisher, the Shapton 16K & Gok20 also can be very good in this category.
J-Nat Suita finish another, very good option on some edges.
For me any edge that I can still comfortably shave off of will work and my best efforts have come from edges that are keener than 8K.