Jack, I don't understand what you mean by hour-glassing, but the only trouble I had with the Code 0 was that I could not have it permanently set I mean in the furler. with winds over 20K I would have to take it down (already furled) and I just tie it along the side of the boat.
The problem was that with the wind force the very thin fabric was pulled out and even without unfurl it got more tight and that means that some considerable part of the geenaker come out and start flapping on the wind.
The other problem was not really a problem but a limitation of that sail. It is not really a downwind sail. It cannot take more than 15K wind. When I started to have fun downwind I had to put it down, afraid that it blow away.