I wondered about that. Once I get the outer box formed, I should be able to attach some finer window screen inside it. I was just worried that this might restrict air flow too much but apparently not. Makes me wonder how so many people can just go without the box altogether. I appreciate the correction though. I need all the tips I can get. Right now, it's this forum, a few conversations here and there, and Tractor Mike on YouTube. Learning a lot!