ブルーハワイ炊き込みごはん what spine mode are you using ("lock-hip" "lock-head" "lock-both")?

Some info: There will be some amount of expected difference at the chest when using and not using a chest tracker because you're able to take control of that bone via tracking. The bone will bind relative to the tracker at a position determined by the avatar's TPose. If the TPose has the chest forward, the default chest tracking position will also have it forward. Lock-head and lock-both spine modes also use the TPose to influence the IK result. Lock-hip however does not. If you're switching between lock-hip and lock-both for example when taking these screenshots, that would account for most of the discrepancy.

For more context on why the TPose has more influence over the spine, you can see this Canny: https://feedback.vrchat.com/vrchat-ik-20/p/chest-bone-gets-moved-back-when-its-not-directly-above-spine-tilted-a-bit