Doing a lot of street photography and travel photography, and getting a new (to me) 5d and the brick, I wanted a grip strap for securing my hold. I don't want to add a grip (size and weight). I also wanted to retain the use of a neck strap for shoulder-carrying and for lens changes.
I researched it here and learned of the camadapter rig. I purchased the adapter and grip. I got the one with the Manfrotto RC2 quick release.
The QR works great, the grip strap fits great. No need to remove the unit to change the battery or for mounting on the tripod. My 5d feels secure and the weight of the brick seems to mostly disappear. The only issue is I have to retrain my finger to reach the adjustment wheel behind the shutter. I reach it fine but a slightly different angle.
Thanks all for the great forum, the helpful advice, the usually friendly environment and the wealth of knowledge.