When i've had that issue I copy the ID of an avatar I already have uploaded that i dont like or use and i put it here (the pic below)
[image: Screenshot 2026-02-12 061728.png]
You can also use the lattice tool for Unity. I find it helps a lot.
Link: https://forum.ripper.store/topic/77591/gift-unityeditor拡張-非破壊ラティス変形ツール-lattice-deformation-tool?_=1768952812950