My first thought was right on the line of Carl's...he just put my thoughts into pictures much better than I'd have been able to describe it. Looking forward to seeing what you come up with. You always build such nice fixtures.
BTW, off topic a bit, but you wouldn't happen to still have a good square chunk of tool steel laying around welded to a stem designed to fit in a hardie hole of an anvil owned by a certain acquaintance, would you? If you did happen to have it still laying around, I'd be very very interested in compensating you for your time and materials for the possibility of seeing said hardie block. And if that material has been sourced for other projects, absolutely no problem. Shoot me an email sometime (I think my PM box is full).