I am going to move up to a 7D from my 50D, weatherproofing being one of the major reasons. Will also be buying a grip and wondering what that does to the sealing out of water/dust? Have used non-canon grips on my other cameras, but weather sealing was not a concern. Do I need o buy the Canon grip to maintaain integrity of the seal? Anybody have a non Canon grip for a 7D? Is it sealed around the battery door opening?