I have recently had a chance to "touch & feel" both the D4 and the D800 at the local Camera Mart just north of Troy, Mi. I found the D800 much 'smaller' in feel compared to the D4. It has been a number of months since I had a chance to "touch & feel" the D3s at B&H during a quick visit to NYC. The D800 'feels' more like the D7000 to me. My preference would be a D3s/D4 body size compared to the D800. And I am concerned that my 'holding technique' might be a challenge based upon my 'advanced age.' Many thanks to all for their candid comments and advise.