Clinch Valley, I have heard Greg Judy say "don't worry about a back fence in winter", but I have often thought that your pie shaped paddock would work. Only draw back I fear, from a strictly hypothetical perspective, is improper distribution of the animals. I suspect that some areas might get destroyed while other areas might not get grazed enough. Also, fence costs per acre is higher with a triangle than with a square or rectangle. But that may be a wash when taking into account the extra fence needed to provide a lane to water. Judy can make a good case for either square or rectangle depending on producers aims, so maybe shape plays a greater role than many think. Maybe someone has tried it and can share.