>>294589806
Yep, fbt makes the hip the root of the IK rather than the head. The local shrinking of the head bone to 0 usually prevents your model from clipping into your view during your walking animation but if you playspace move up or down it can clip.

With sufficient autism you could in theory configure your own separate VRIK script from finalIK on another copy of the armature and use unity constraints to get the tracker and headset and controller positions from the original armature, but I don't know if it'd be that different than vrchat's configuration in the end.