How to Retarget Arm-Only Animations to a Humanoid Character?

Hello,

I’m currently trying to retarget an arm-only animation to a humanoid character. However, the hierarchy of the arm-only skeleton is quite different from that of the humanoid. I’d like to confirm if the approach I’m taking is correct.

The retarget chains on both sides seem very different, especially regarding the position of the root bone and the pelvis. If I were to implement a first-person FPS, would it be better to simply use the arm-only player mesh that existed in UE4?

If I’m misunderstanding something or doing this incorrectly, I’d really appreciate any guidance. Thank you for reading and for your help.