thank you very much Drongle for your reply, but i need a very complex physic shape for my model, so i think i will try to add cubes at each vertex of the bounding box reference just for preserve the proportion of the physic shape.
* Edit:
Anyway, the point to upload a physic mesh is to create an exact shape were the avie can move, the physic mesh can be different from the original shape for many reason, for example i can create a mesh with details that i will not include in my physic shape. for an experienced 3D modeller it's easy to work around with a boundig box references.
Anyway a bounding box reference is an artifact, not a optimal way to work, consider to fix this bug. Added on Jira:
https://jira.secondlife.com/browse/CTS-661?