This is very similar to quintessential medium height (thanks madmaster) and I expect multiple people to come up with similar solutions.

18R is what I believe to be the lowest rate with a reasonable latency at min height. My previous solution takes 3 salts from the input every 10 cycles and got 135C at 20R. This one takes 4 salts from the input every 12 cycles which reduced the rate to 18 but increased the latency due to awkward input to output ratio. Still saved 5 cycles overall.