Battery grip question
In previous pro cameras, especially Nikon, the addition of a specialized vertical grip power booster combo actually increased the camera's speed. You can do this by using variable DC servo motors in the camera. The advantage is the higher the voltage the faster the motors turns. The grip passes a higher voltage to the camera motor drive circuits while the rest of the electronics stay at 5v or so.
Unfortunately Pentax never wanted to do that so they have never had a camera with a frame rate over about 6.5 fps I think, while Nikon and Canon have had ones that did over 10 fps and in some cases almost 15 fps (mirror fully locked up).