Yes. The RR stem gives the rider more confidence, more control, and subsequently allows them to ride faster. On a trail that I am very familiar with and can do runs that differ by less than 2 seconds run to run, I was able to do back-to-back runs consistently about 15 seconds faster over 3 minutes and 20 seconds. This was on the same bike run to run only changing the traditional 50mm stem for an RR stem. This was true over multiple runs on the same day, across multiple bikes with differing geometries in subsequent tests, and similar time gaps were found on other trails too.