the tests with opentrack are giving a different result...i suggest you try it...
i dont get motion sick at all with a slight oversampling of the pitch and yaw axis....and a 1:2 oversampling is really not needed....maybe something like 1:1,3 is all you need to check your 6 without neck strain...and with such little oversampling your brain, or at least mine, has no problem to be convinced that the motion is correct...i dont get sick at all....
this is not true when watching a track in the rift, where a few seconds are enough for me to feel uncomfortable...its really something different....
the only problem with opentrack and dcs is, the way how track ir is implemented with artifiical shoulder size and the tendency to move around the z axis when looking back trying to lean left or right...thus moving around the wrong axis...if i could get rid off this behaviour i would be using opentrack all day long, as the oversampled pitch and yaw axis are absolutely no problem whatsoever and actually feel totally natural....