Suggested BVH Hip Y Locations
From Second Life Wiki
It is important to know how far to place the hip above the ground to avoid floating over it or sinking under its surface, unless that is desired in your animation.
It's obvious that the location the hip should be in depends on the pose the avatar is in. Therefore this article can only indicate a reasonable range for some common situations.
It's also obvious the distance between the hip and the ground can vary depending on the standing height of the avatar. Fortunately, Second Life adjusts for this.
The lowest hip locations are usually used in ground sit animations. The built-in ground sit animation uses 8.325 as the hip Y location when fully seated on the ground.
The highest hip locations are usually used in standing and turning animations. Second Life has 5 built-in standing animations, all of which are motion captured, so there is no fixed Y location. However, all values are close to 42.100, and that value works well for all shapes I have tested it with.
All other animation types where the location of the ground is relevant (walk, run, prejump, crouch, crouch walk, land, and stand up) will be somewhere in-between.
A bug causes avatars to float above or sink beneath the ground when using custom sitting animations (see VWR-25037).