[Moth]

Your fins slumped because they were so close to the elements. The elements in any kiln fire to raise the temperature in the kiln to stay within a certain parameter of degrees controlled by your thermostat. The elements themselves, when fired up, are hotter than the temperature you have with your thermostat. If you put thin little pieces of glass too close to the elements they will easily slump.

I have an old radiant coil waffle iron that I was trying to use to preheat big rods and boy did that thing ever get hot. Too hot. It would slump the rods even though the elements were much thinner than kiln elements.

Made excellent waffles though.

Under normal conditions, your Glass Hive kiln won't do that to your soft glass turtle flippers if it is programmed for soft glass temperatures.