Interesting thought. For the last few seasons I have skiied on nothing but midfats, and fats. I really think I could ski only on a fat, especially a short(165-170)twintipped one. Here in Mammoth some of the best skiers ski fats all the time. I use my mids (173 Enemy) most of the time, but sometimes I will use my fats (180 AK Launcher) for weeks on end, especially when it dumps for a month or so. Both skis seem to do everything well. This season, I am getting two pairs of AK's, a 165, and a 180. I am betting the 165 will become my every day ski, but we shall see. I have a pair of 165's mounted randonee that I skiied all the time last spring. They were great everywhere, so I am pretty confident in that lenght. I think that If K2 made a twin tip that was 80cm underfoot with the four sidecut (ie; an Enemy that was 5cm wider) and came in a 170, that it would be the only ski I needed. by the way, I love windbuff, bumps, pow and crud. I tend to just ride the edge out on the groomed to get it over with and back to the real stuff. I don't see any reason for most people to ski on anything but a mid or fatter.
I think mid fat is 70-80cm underfoot, and 81+ is fat. What does everybody else think?