Frank, I can't help you completely. However, many years ago I was in the cutting room at Western Mountaineering. They had a down loft device. It was a clear plastic cylinder that was full of down, and it had cubic inches of volume lines marked on the sides. There was a round cap on the top end, so one ounce of down would be placed into this, and it would expand to push the round cap upward in the cylinder to some mark. Back then, 600 or 650 FP was a big achievement.