I remixed Nathan's brushless gimbal for hero 3 to fit my needs. Because I have a Hero 2 and different motors(rctimer 2212-70T) it had to be redesigned. If you want to use it on a TBS discovery you can use a different frame mount.
It is perfectly balanced for a hero 2.
UPDATE!: Updated the 90 degree arm. Now it is 8mm thick instead of 7mm. This should remove the 'wiggle' which causes jello when printed in ABS because the old 7mm version lacked stiffness. Maybe if you print it in PLA you don't have that problem, havent tried that yet.
Also added a mount for the CCD cam, martinez control board and video transmitter.
I am still waiting on 1 motor before I can do some testing!