I have an old leather fly wallet that I picked up somewhere in my travels, complete with flies. My observations are twofold. 1. The flies become "crushed" and flattened, and, 2. the wool material holds the moisture which leads to rusting hooks. I can only imagine what it would do to a beautifully tied deer hair popper. I think that there is a reason we no longer use leather fly wallets ever since fly boxes became available. Just my two cents worth.