When Ken came to help me Monday afternoon I told him about my experience with the downdraft in the high wind. When we started discussing a Venturi effect solution he said he recalled seeing some devices for chimneys whig worked like that.
It was one of those cases where their is a hiatus in my knowledge. Sure enough, when I looked for information it was right there. These are two references and there are a lot more. If I do decide to eventually change the flue cap, I won’t have to reinvent the wheel.