Great discussion! It has made me rethink my decision to put slightly beefier tire on the back wheel. I ride on rough and occasionally rubble-y roads, and my thought was that I should have a 32mm wide on the back and a 28mm on the front, so that the stiffer and more heavily loaded rear triangle would have more tolerance before I experience a "pinch flat" on the rear if I fail to "post". The trail discussion changes my thoughts - a slightly larger front tire would mean a slightly larger trail and therefore slightly more stable steering - though I think that for large size wheels, the difference will only be slight.