Update - not all boats are built equally. Some have really nice "owners cabins" and the same boat might have a much smaller double. We did a trip a couple of years ago with four couples, and to make it a little fairer the couple that got the large owners cabin paid about 5% more than the average cabin cost, and the couple that got the smaller cabin paid about 5% less. Both couples were very happy with this arrangement. YMMV.