Updating collision bodies

I have a cube I built in blender, exported using ogre into its xml file. I import the xml into my game and load it, attach a control shape and a compoundcollisionshape. I have it set up to where I launch a cannonball and on pact I pick a couple random triangle and change thier vertices with a vertexbuffer. I call updatebounds () and updatemodelbounds () and setcollisiondata () but the collisionShape doesn’t cover the effected vertices. Am I missing a step?