Thanks for the help , I am getting really nice results!
I am developing the setup also using vive tracker for shoulders and spine and everything is working fine.
I was only wondering if there is a way to recall in the blueprint the unique ID for each tracker, I see in SteamVR Manage Trackers each one has a kind of serial ID.
For now I am using the device number IDs but everytime I start steamVR it changes and I have to manually find the correct numbers ID for each one.