I along with many others have been "Speed hacking" servo's for quite a while now. The best servos we have found so far are the supertec pico, the multiplex ms-x1 and the supertec s136l/2bb (this one is 33g so is not suitable for micro flight)
The pico and ms-x1 both weigh 6g(ish) and have a 5gear gear box.
Here is a link on how to speed hack them.
I am not sure if it is possible to remove the 2 gears which are no longer used i will check in the morning.
I hope this helps
Ian Mc Donald
(p.s. the guide says "this guide assumes the servo is already modified for 360deg controlled movement". This is what we do in robotics to make the servo's go continiously around by disabeling the pot. Leave the pot as it is and you will be fine)