Size wise it's close, a comparison on Dpreview shows the MkII is 1mm wider, 1mm higher and 4mm deeper. The real problems I see with putting the MkII in the old 7D housing are:
- I often use the custom settings on the mode dial. On the MkII you have to push a central button to turn the dial, there is no facility to do this on the original 7D housing.
- The two controls I use most on the back of the camera are the "Q" button and the joystick control, the Q button is in a completely different place and the joystick control is slightly higher on the MkII so they're not going accessible with the MkII in the original 7D housing.
- My wife wants to takeover my 7D when I upgrade to the MkII and I won't have the old housing anyway