I made some tests and with the newes versions You must turn HMD MIRROR ON and there are better performance with Extended mode. With the previous versions I could use HD resolution using Direct mode so I had stable 75 FPS and I don`t needed FullHD. With the 4.7 UE and 4.4 Oculus using Direct mode I got 37 FPS all the time. The best combination for me is: Unreal 4.5.1 and Oculus 4.2 with Direct Mode and HMD MIRROR OFF.
Another thing is that I am forced to use 0.4.4 Oculus Drivers in the newes 4.7 Preview UE. Why is that? Why I cant use the older drivers which were better in performance? Strange thing.