Per the dev logs, it is already 90hz on the quest 2. If you are feeling motion sickness, it’s likely not the hz, its the fact you are in a plane going through all kinds of motion. Until you are used to it, ensure you stick with the first two difficulties as they don’t allow loops and inverted flying (which should be easier on you). As well, there are some really cool comfort options to help those with motion sickness issues, however I’m not sure if it’s in the demo. Go ahead and have a look in the options. If it is there, I’m not certain if it’s as advanced as the current build (the previous version just made your POV smaller within a box, now it’s more dynamic).
Hope this helps