I came to realize that the jello effect is actually due to camera vibration. When I mounted the camera using the plastic mount I could rock it left and right a little. The problem is the mating between the mount and the camera. Yesterday I built myself an aluminum mount using scrap angle and plates. This afternoon I did a flight test. The area was quite bumpy and wind gusted 20 kts at 80 degrees. The quality of the video is not perfect due to the rocking of the airplane. However, there is very little jello effect. Here is the video and photos of my mount.
Drift camera mount test video

Use epoxy mixed with micro balloon to level the bottom of the mount. Use a hardware store 1/4-20 ss screw, washers and lock washer to hold the camera to the mount.