As I said speculation. The 7D and 5D already use 35mm lenses and so there is no change in focal length. A 50mm lens is a 50mm lens ... Do you know how much the sensor is moved? ... [a href=\"index.php?act=findpost&pid=52633\"][{POST_SNAPBACK}][/a]
The larger size of a 35mm format sensor compared the current roughly 16x24mm K.-M. ones is fact, not speculation, and the weight increase is a fairly inevitable consequence.
I do not have to know how much the sensor is moved to know that with sensor size and focal length 1.5x greater, it has to be moved 1.5x further. (K.-M. did demonstrate quite substantial movements for the 7D sensor, maybe half a cm. Optics and a few observations about camera shake can give a fairly god idea of how much sensor movement is needed with a given focal length; unfortunately for 35mm format the movements are far more than the movement of lens elements needed with "in-lens" stabilization.)
I already said that it is not impossible, but unlikely on the bases of the clear facts are that it would be significantly more difficult.
Focal length choice is dictated mostly by desired angular field of view, so that larger formats are mostly used with proportionately longer focal lengths. That is where the need to move the larger sensor by greater distances come from.
If instead you try to use the same focal length with a 24x36mm (35mm) sensor as would work with 16x24mm sensor, the image of your desired subject is the same size, and so fits into a 16x24mm crop from that bigger sensor. So cropping to that desired image discards any possible advantage of using the larger sensor. That is not the way larger formats are used!
P. S. I would love to have a dime for every digital format comparison which implicitly assumes or even explicitly claims that different formats will typically be used with the same choices of focal length, aperture ratio, exposure index, despite massive evidence to the contrary from throughout the history of photography.