I read somewhere that those box fans can move like 2000 cubic feet of air per minute if you seal the edges right. Might be worth a shot before dropping cash on a real solution.

Kept my gym membership for the same reason. Anchors work.

That 3/8 inch gap is basically the manufacturer's way of saying "good luck, you're on your own now." I bet that bracket set cost double what a simple metal post bracket would have been too. Probably came in a sleek box with a drawing of a perfect fence that somehow looks nothing like the one you're actually building. Next time I'm just using a hammer and some nails, at least that gap will be my own fault. What exactly did you end up doing with those brackets, use them for target practice?

Call it a seaming iron not a carpet iron.

And I thought my 45 minute rant about power levels was bad.