Here is a short dive i did down the river with the Gopro shooting in 60fps. I sent it to Motion 4 from FCP and then with Optical flow on changed speed to 15%. Then exported it and conformed the frame rate in Cinema tools to 23.98fps then imported it back into FCP and then cut it up to show full speed mixed with the new slow motion. Compared to 15% speed in FCP this is outstanding.
Enjoy
Enjoy