I have purchased and installed a Bis Ultima. My brother has a Pacific, and we both have 6" insulated pipe for our chimneys. Even with his cap on, my brother has had issues with birds getting stuck in his chimney. I am going to button my cap up in the next couple of days and hope to figure out a way to avoid this. My dealer gave me some chicken-wire like stuff, but we think that it would wear away over time. Any suggestions?