With the Oculus Rift the frame rate is capped. Apparently nothing can be done about it (but reverting to an older Unreal version and Oculus Development Kit).
Low frame rates makes accurate physics hard or impossible and introduces lag. Substepping works partially but really only affects physics and limits game code possibilities a lot. Custom physics is complicated and limited. A lot of problems arise when several threads, timers and tick groups are used.
Substepping - running the physics faster than the game tick - could be supplemented by “hyperstepping” - where the render thread would only be called every second, third or else tick. Then all the normal game code would just work at e.g. 120fps, 180fps, etc and the rift would still display 60fps. Slower frame rates would of course work, too.
Substepping could be combined with hyperstepping. The hyperstepping does update everything but visual display and substepping does only do the physics in between.
Would it be hard to implement this kind of change into the engine. Essentially only the render thread shouldn’t be called every tick (and frame times have to be adapted to get actual 60 fps on the display).