Setting the defaultdeviceprofile r.MobileContentScaleFactor to zero did help in my case, don’t know why this is not the default on GearVR. Didn’t see a noticeable difference setting the texture compression to UserInterface2D instead of the default DXT1/5, instead.
What would really be useful is the support of the OVRLayers, that according to this thread should land in 4.11:
https://forums.oculus.com/viewtopic.php?f=60&t=26700
Anyone has more info about how this was implemented and how to use it?