A37575 - JH is simply describing a form of SI used all the time in simulators - not 'a problem' - and you will have experienced it on every detail. It is the use of a tilt of the box to simulate a longitudinal acceleration, that's all. It 'stimulates' all the body's acceleration sensors including the inner ear. As an example of the power of SI, it is extremely convincing, as we all know. The point JH is making is that if you 'reverse' the 'illusion' it can be equally convincing.