Quote Originally Posted by Ole
With a lens that big and heavy, wouldn't it be easier to make a camera back and mount it to the lens? A strong cradle for the lens, a lighter one for the back. Bag bellows between. Since the "camera" wouldn't be carrying the weight of the lens, it can be much lighter and simpler.

Just a thought...
My drawings are abysmal, I know. (did you see them on the second page?) Let me try to clarify: the lens and frame is one piece attached to the tripod block. The back moves back and forth on the rail on the and is not stressed.

Here's a larger sketch. The bottom shows a shadow where the tripod screw goes into the block. http://elearning.winona.edu/jjs/proto/NW13.jpg

The tripod block is at the balance point and can be moved a bit left anyway.

A bag bellows is a good idea. Thanks!

Dunno. Is that more clear or am I still missing something?