Since it came to me, here is my 2,000km ride impression.
It is good and excellent product, smooth riding around 20mph. Though I'm not climber but enjoying 60miles day at weekend and vacation season around Japan nationwide. Stop and go at signal is much easier than before ( Roval Alpinist CLX) and reaching to cruising speed is faster. And cross wind and head wind is no more a big concern while riding, much stable and controllable. Climbing at 3%-6% is no problem, and sometimes feel much comfortable than Alpinist CLX, maybe because "sitting" is my favorate style ( I do not like dancing...).
I have rim brake Roval CLX50 with S-Works Tarmar SL6. I think RCX is a little bit stiffer than CLX50, but riding feel is similar. This wheel really fits to my riding style, with my partner S-Works Aethos.
One negative point is its surface is not matt... so small scratch is easily visible...
By the way, I could not find another PARTICLE at Shimanami2026, which is a bit sad...
