A quick note to let you know I’ve just posted the following in “My VR Settings - G2”:
[Update 02JAN2021 - Settings for Motion Reprojection]
NB: although it is not Index or SteamVR related, and I didn’t try some of these findings with the Index yet, it is possible the NVidia CPL Settings, the rationale behind the FS2020 settings change and the workaround to the FS2020 bug affecting motion reprojection (and not just) could be helping flying in VR with the Index with SteamVR Motion Smoothing.
PS: you might not know this but WMR OpenXR preview (v105) includes a new Motion Reprojection mode capable to extrapolating up to 2 frames. This makes it rendering 90fps from 30fps and in practice it is working nicely once you’re working around the limitations (see my post) and you can bear with the artifacts.