I'm using FCPX 10.2.2 with L&L (version downloaded yesterday). I own SliceX and TrackX but have been looking for a reason to pick up L&L so I gave it a whirl on this short clip of Turkeys behind my house. In the video below, I compared 3 clips, 1 with no stabilization, 2 with FCPX Stabilization and 3 with L&L Stabilization with Rolling Shutter. I made NO adjustments to either clip or stabilizer beyond setting the camera to the iPhone 5s in the L&L settings. Everything is default. On the FCPX side, I just ticked the button to turn it on. I notice quite a bit more warping and distortion with the L&L Stabilizer and would love some help to better understand what adjustments I should be making. Thanks much!
The distortions in the L&L stabilized video are mainly caused by shutter distortions or an incorrect shutter correction coefficient. Did you capture this video with an iPhone 5s?
You can try to adjust the shutter coefficient ("Custom Coefficent") manually. This should give better results.