1. When i set the cones collision shape to cone it appears to construct a shape that is larger than the original shape.
You can see this in action if you run the app, then press spacebar to drop the hoop, then press C to change the cones collision shape from cone to static mesh. The hoop will fall a little further and contact the cone
2. When the hoops compound collision shape is set to anything but a sphere, then the collision shape appears to extend beyond the shape specified. you can see this a couple of ways
2.1 Run the app. Press H to change the hoops compound shape to cylinder. Press C to change the cones collision shape to mesh. Press SPACEBAR to drop the hoop. You will see a fairly large gap between the cone and the hoop
2.2 Run the app. Press H to change the hoops compound shape to cylinder. Press M to move the cone out of the way. Press SPACEBAR to drop the hoop. Move the mouse over the grid and bump the hoop with the red cylinder
2.3 (My favorite) Run the app. Press H to change the hoops compound shape to cylinder. Press M to move the cone out of the way. Press SPACEBAR to drop the hoop. Press the DOWN ARROW until you are level with the hoop. Press ENTER
