Valve released a beta version of Steam VR today which includes per-application frame rate locking. Based on my quick test flight, this appears to be a game-changer for MSFS in VR (and for complex sims generally).
I set a target frame rate of 40, and after some initial hitches, things were incredibly smooth in flight. Before I’d get bunches of stutters as the game constantly struggled to hit the headset hz. Now, just a smooth, consistent frame rate. 40 in VR is obviously not fantastic, but seems perfectly acceptable for civi aviation, and it now feels much more like what I am used to in something like Elite Dangerous or IL2.
Motion smoothing is still pretty wonky and a no-go for me, but this is a great starting place. The frame rate was so smooth and stable I can now look at upping the settings and improving the visuals.