Does anyone have any personal experience with 9 point tracking for full body tracking?

I assume the extra 3 trackers go on your upper arms and then the other on your chest? does it make massive improvements or is it barely noticeable? I figured the IK can "estimate" just fine where your chest and arms are without these 3 extra trackers so I always doubted if it makes any major difference. It seems cool to have even more 1:1 movement, but Idk at all how it actually performs. I only have regular FBT hips/legs