Did a quick test this weekend. I wanted to see if you have a player 9 swf and load it into a player 10 swf, if there could be any issues. Mainly, I wanted to see if there could be problems with the new 3D properties in player 10. So I just created a new player 9 swf that had some five3D elements in it, so essentially I had an extension of the Sprite class with properties such as z, rotationX, rotationY, and rotationZ. Since player 10’s Sprite class contains these properties nativity, my theory was that importing the player 9 swf would throw errors because now those 3D properties of the five3D elements would not be properly overridden. This is exactly what happened. Good to keep in mind in case you ever run into a situation where you might have to load an older flash 9 swf into a newer flash 10 shell.