It's actually very easy. Do a calibration with the camera platform flat and level, use a bubble level to make sure it's absolutely level side to side and front to back before clicking on the calibrate button in the GUI. Now swing the camera platform forward or backward so that it is 90 degrees from flat and level, basically the camera would be facing either straight up or straight down depending on which way you swing the platform, for calibration purposes it doesn't matter which way you go after doing the basic calibration. With the platform in the 90 degree position click the calibration button again and wait a few seconds.
Now swing the platform so it's exactly opposite where you just did the calibration and once you have it there and at 90 degrees do the calibration again. Return the camera platform to flat and level. Now you need to swing the platform right or left until it is again at 90 degrees to horizontal, in other words tilted sideways so the bottom of the camera would be vertical. To get to 90 degrees on the sideways or roll axis you need to do what Gotheli describes in post #275, or you can just lift one side of the multi once you have maxxed out the rotation of the platform on the roll axis, either way get it to 90 degrees from horizontal to either right or left and do the calibration again, then swing it all the way to the opposite side, get it to a full 90 degrees, and calibrate in that position.
Last, turn it back to flat and level and then go 180 degrees around so the camera platform is completely upside down, make sure it's level in that position and do the final calibration, you have now done a full accelerometer calibration and can bring the platform back to its normal position.
After doing that Friday evening I went out and flew at few different locations Saturday morning recording video at each. It was the usual gusty wind blowing and at each location the there was a large enough open area for the wind to be in 8 to 10 mph range, enough that the frame was visibly bouncing around but the video stayed amazingly steady. Still had a bit of an issue with horizon drift but I had changed some settings Friday evening and apparently missed the setup.
Today I tweaked the settings back towards where they were originally, made a few changes to wiring, and setup the HDMI downlink again after modifying the cable to work with the gimbal. Biggest difference is the power to the gimbal is now a constant 12 volts supplied by a CC BEC Pro connected to the power distribution board so the power level stays constant through an entire flight(s).
Just charged a battery and did a test flight out front and the horizon drift is gone! Quick turns, flying sideways, anything I tried didn't cause the tiny level of drift I saw yesterday so I'd have to say the full accelerometer calibration, tweaking the PID motor power settings slightly, and providing a regulated supply of clean power were the last pieces of the puzzle, it's rock solid Zenmuse like performance now.
Time to do a full tuneup on the Cinestar itself and then get out in the field and record some video. I finally have a setup I like and can use without worry about video quality after over 2 years of trying most everything under the sun and not getting the results I wanted
Ken
