Nice! Looking forward to hearing how you like it. I just picked up a lightly used '06 WR125 and plan on putting the WB165 kit on it, hopefully sometime next spring.
In the meantime, new springs are in the garage, and am waiting for the fork valves to return from a tuner. Once the suspension is done, considering a APT SmartCarb, or Lectron. Then the 165 kit.
Meanwhile, the bike is a hoot to ride as a 125. -Ed