FYI - Here is a "Strong-Hand Shark Clamp":
http://www.stronghandtools.com/products/sharkclamp.html
I found the 5" straight handle one at a Harbor Freight retail store for about $15. It is great for reaching around the neck and pinning down neck joints or shoulder ribs or such. The pads are rubber faced and articulated so they stay securely clamped on angled faces or even across joints.
I had tried every kind of clamp in my shop and could not find one to hold a replacment upper bout to the block for gluing (the top was still on). This did it easily. I am going to order a larger one as well. Unfortunately even it will not reach from fingerboard to button.