We recently installed the HXT9610 Metal gear retract servo from Hobbyking in our Kyosho Focke Wulf FW-190. It runs really smooth and works great. Check out the short clip.
We will post a full review later this spring.
Parts we used:
Hobbyking HXT9610 Low profile metal gear retract servo
Kyosho SQS Warbird Series Focke Wulf FW-190 50EP