the center of ConvexHullShap

[Yan-Xiaodi]

I create a box use the btConvexHullShape，code is this:

{
    static btVector3 vertices[] = {
	    {0, -1, 0},
	    {1, -1, 1},
	    {1, -1, 0},
	    {0, -1, 1},
	    {0, 1.0, 0},
	    {1, 1.0, 1},
	    {1, 1.0, 0},
	    {0, 1.0, 1},
    };
    btConvexHullShape* convex = new btConvexHullShape(&vertices[0].getX(),
														    sizeof(vertices) / sizeof(btVector3),
														    sizeof(btVector3));
    convex->initializePolyhedralFeatures();
    //btCompoundShape* compound = new btCompoundShape();
    btTransform ConvexTransform;
    ConvexTransform.setIdentity();
    ConvexTransform.setOrigin(btVector3(btScalar(0), btScalar(0), btScalar(0)));
    //compound->addChildShape(ConvexTransform, convex);
    btScalar mass(1.f);
    
    m_collisionShapes.push_back(convex);
    auto body = createRigidBody(mass, ConvexTransform, convex);

}

and I got this

when I move this box,it appears not like the box created by boxshape,it seems like its mass center is in the edge of the box，when I try to Flip the box,it will Flip back, it seems like its mass center is not in the center of box which I hope for. what's the matter with that?I have google for this problem.and I got the some similiar problem.
the key word: CompoundShape btDefaultMotionState to set the m_centerOfMassOffset
here is the website:
https://pybullet.org/Bullet/phpBB3/viewtopic.php?p=6244&f=9&t=1506
https://pybullet.org/Bullet/phpBB3/viewtopic.php?t=2209

I have tried all of them , but it not works for me, maybe I didn't use it in the right way,I am fresh with Bullet.
I hope someone could tell me how to fix that ,how can I do to make sure the btConvexHullShape has the correct center of mass like btBoxShape . Thanks a lot