Like I said. You guys are going off topic here. Print size and viewing distance have nothing to do with the full frame vs. crop question. That is entirely something of resolution. Since a crop sensor "may" have more MP density, then your assumptions of another topic would be correct. In the case of the d800 and a 15mp crop camera, there is no difference in COC, when every other factor is equal and the d800 is cropped to 15mp in post.
I got to agree with this. While statements of print sizes and perceived DOF are true, it's veering offtopic BADLY and this topic takes a bit of understanding before you can tackle that one. It's sending mixed signals IMO. Large print vs small print is no longer apples to apples comparisons... might as well be comparing color depth and resolution at that point.