From this angle, it appears that the D-BG4 has added so much in "depth", I guess that's what it takes to accommodate six AA batteries...
http://www.digitalcamera.jp/html/Hot...4/K7-026-L.jpg
And from the side:
http://www.digitalcamera.jp/html/Hot...4/K7-020-L.jpg
This shows how big the grip is compared with the compact size of the K-7 body:
http://www.digitalcamera.jp/html/Hot...4/K7-007-L.jpg