More arms than R. The major hurdle to getting to 18R here is to avoid collision when arm 19 does the last swing, which means that the vitae has to have extra waiting instead of being driven by one pseudo-6-loop arm. It also means that I couldn't find a design to assemble the product the other direction (quicksilver-vitae-silver instead of silver-vitae-quicksilver) to get 3 free latency.